[18] §. 1.

§ 1

Vitellus, ovi albumini innatans, tenui serosa membrana, qua includitur, ab albumine separatur et tantummodo chalazis, ut quidem Leveillé[1] opinatur, cum eo conjungitur[2].

The yolk, floating in the albumen of the egg, is separated from the albumen by a thin serous membrane by which it is enclosed, and only joins to it by chalazas, as in fact Jean Baptiste Leveillé is thinking.

In superficie vitelli exigua quaedam albida macula conspicitur, quam cicatriculam vocant, quae licet ab omni inde tempore sat nota fuerit et a diversis autoribus diversa acceperit nomina[3], nondum [19] tamen eo scrutatores permovit, ut et ubi sedeat, et unde oriatur, accuratius investigarent.

On the surface of the yolk is visible some small white patch they call cicatricle, which, although enough known from a long immemorial time and received different names by different authors, nevertheless it has not yet pushed the researchers to investigate in more accurate way both where it is situated and whence it originates.

Observavimus autem,

1) vitelli membranam in hujus maculae regione singularis esse tenuitatis et pelluciditatis;

2) magnam differentiam intercedere inter cicatriculas ovorum ad incubationem aptorum et eorum, quae nullam pulli evolutionem admittunt.

Actually I observed that: 

1) the membrane of the yolk in the area of this patch is unusual for thinness and transparency;

2) a big difference exists between the cicatricles of the eggs proper for incubation and of those not allowing any evolution of the chick.

In ovis ad incubationem ineptis macula minor, albidior, granulosa, non perfecte circularis apparet, et ab exigua albidae materiae gleba producitur, quae reliquae Vitelli massae immersa inhaeret, et ab illa praecipue colore distinguitur.

In the eggs not suitable for incubation the patch appears smaller, more white, grainy, not perfectly circular, and sticks out from the small mass of white matter that immersed adheres to the rest of the mass of the yolk and is distinguished from it mainly for the colour.

In ovis contra incubandis macula haec major, diametri fere duarum linearum[4], plumbeo-albida, perfecte circularis apparet, vitellum autem, ubi proxime eam [20] circumdat, zonulam mox angustiorem, mox latiorem coloris saturatioris efficit; sed macula ipsa pallidiori margine circumdatur, et non raro minorem albidiorem circulum includit; semper autem ejus centrum punctum albicans occupat.

On the contrary, in the eggs to be incubated, this patch appears greater, of the diameter of almost two lines <- around 4.5 mms>, of leaden white colour, perfectly circular; the yolk, where surrounds it nearby, creates a small area now more narrow now wider of more saturated colour; but the patch itself is surrounded by a paler edge and not rarely holds a smaller and more white circle; but a white point always occupies its centre.

Vitelli membrana detracta, facile comperitur, maculam praedictam progigni singulari strato, e minutissimis granulis lentis acie conspiciendis composito, discum tenuem referente, quod vitello ita impositum est, ut superficie sua interiori hoc, superficie autem exteriori membranam vitelli tangat. Facili negotio stratum istud, quod libenter membranam vocaremus, nisi nimis molle esset, a subjacente vitello elevatur, excepto centro, quod subjacenti glebae, simili illi, quam solam et nudam in ovis non incubandis invenimus, arctius adhaeret, ita ut, facta sejunctione violenta, vel gleba vel stratum membranaceum destruatur. Cicatricula igitur nil aliud est, nisi exterior hujus disci superficies, quam hyalina vitelli membrana transparere sinit; albidius autem maculae centrum etiam a praedicta gleba dependet.

After having removed the membrane of the yolk, we easily realize that the above-mentioned patch is born from a particular layer, composed by dwarfish granules visible with the acuteness of a lens, similar to a thin disk, which layer is located above the yolk, so that it comes into contact with the yolk with its inside surface, while with the external surface it comes into contact with the membrane of the yolk. This layer, that I gladly would call membrane if it was not too much soft, is lifted from the underlying yolk with little work, except the centre, that sticks in a rather close way to the underlying mass similar to it we find alone and naked in the eggs not to be brooded, so that, after having done a violent separation, the mass or the membranous layer is destroyed. Insofar the cicatricle is only the external surface of this disk, that the hyaline membrane of the yolk allows to shine through; also the centre of the patch, that is whiter, drifts from the aforesaid mass.

Quae cum ita se habeant, haec duo circa cicatriculam distinguimus.

[21] 1) Discum vel stratum membranaceum et

2) glebam centralem ipsi subjacentem, quam in posterum Nucleum cicatriculae appellabimus.

While such things are so, around the cicatricle we distinguish these two things.

1) A disk, or membranous layer, and

2) a central mass located below, that subsequently I will call nucleus of the cicatricle.

Quod autem stratum membranaceum spectat, id in omni pulli evolutione summi est momenti. Praeterea enim, quod sibi sedem ac domicilium hoc deligit Embryo, ipsum quoque sua substantia ad ejus configurationem plurimum confert, quare id etiam in posterum blastoderma[5] vocabimus[6].

As far as the membranous layer is concerning, it is of very great importance in every evolution of the chick. Besides in fact, since the embryo chooses this layer as its residence and domicile, such layer also with its substance is very useful to its configuration, which is why also from this time forward we will call it blastoderma.

[22] §. 2.
Hora incubationis octava[7].

§ 2
Eighth hour of incubation

Nucleus auctus est et a circumjacente vitello facilius separatur, cum blastodermate autem adhuc cohaeret.

The nucleus is increased and is more easily separated from the yolk lying around, but it still sticks to blastoderma.

[23] Blastoderma parum increvit; in ejus centro vero, si ab adhaerente nuclei massa caute depurgetur, conspicitur exiguum punctum pellucidum.

The blastoderma has grown a little; but in its centre, if with caution is cleaned up from the adherent mass of the nucleus, a small semitransparent point is seen.

[24] Albumen supra cicatriculam recedit, membranae vitelli ad internam testae superficiem accessum permittens.

The albumen above the cicatricle fades away, allowing the membrane of the yolk the access to the inner surface of the shell.

§. 3.
Hora duodecima.

§ 3
Twelfth hour

Blastoderma auctum, diametri 3-4 linearum, adhaeret membranae vitelli, qua detracta, simul aufertur, subjacentem, cui antea adhaeserat, illibatum relinquens nucleum. Ut igitur examini subjici possit, necesse est, segmentum membranae Vitelli, cui adhaeret, aquae immergi, ubi facile discedit.

The increased blastoderma, with the diameter of 3-4 lines <- 6,75-9 mms>, sticks to the membrane of the yolk, and when this is removed, it is contemporarily removed, leaving intact the underlying nucleus to which it was sticking previously. Insofar, so that it can be examined, it is necessary that the segment of the membrane of the yolk, to which it sticks, is dipped in the water, where it easily separates.

Punctum pellucidum, blastodermatis centrum occupans, pariter ampliatum est, et figura circularis in pyriformem mutari incipit; unde fit, ut jam in blastodermate duae regiones distingui possint, altera interna vel media, quam aream pellucidam[8] [25] cum Wolffio vocamus, altera tanquam zona opaca, hanc ambiens, quam aream opacam vocamus. Area pellucida subjacentem albidum cicatriculae Nucleum clare transparere sinit, quod phaenomenon ad miros errores et icones fingendos ansam dedit Malpighio[9].

The semitransparent point, occupying the centre of the blastoderma, became likewise larger, and the circular aspect starts to be transformed in pyriform; therefore it happens that in the blastoderma two sectors can already be distinguished, one internal or central that together with Kaspar Wolff I call pellucid area <- semitransparent area>, the other as opaque area surrounding the previous, and which I call opaque area. The pellucid area allows the underlying white nucleus of the cicatricle to shine through in a clear way, a phenomenon that offered to Marcello Malpighi* the opportunity to mould marvellous errors and images. 

[26] Quod autem summam meretur attentionem, est ipsius blastodermatis e duobus stratis compositio. Etenim haec membrana ante incubationem ex simplici granulorum, viscositate sua inter se cohaerentium, strato consistit; progrediente autem incubatione, alterum ipsi innascitur stratum tenerrimum quidem, sed eo firmioris structurae, ut circa horam indicatam blastoderma diuturniori maceratione in duas lamellas[10] [27] dividi possit. Interior harum lamellarum, vitello {proprior} <propior>, primitiva, granulosa, in posterum membrana pituitosa, exterior autem secundaria, laevis, omnino {homogena} <homogenea> et aequalis, membrana serosa a nobis appellabitur.

However, what deserves a very big attention is the composition of the blastoderma itself by two layers. And in fact before incubation this membrane consists in a simple layer of small granules sticking among them because of their viscosity; but, with the progress of incubation, inside it another very soft layer is born, but with a structure more resistant to such point that around the marked hour - 12th hour - the blastoderma can be separated in two lamellae by a more protracted maceration. The more inner of these lamellae, more nearby the yolk, primitive, grainy, for the future will be called by me as pituitous membrane <- mucous membrane>, but the more external, secondary, thin, wholly homogeneous and uniform, by me will be called serous membrane. 

Ambae hae membranae totum blastoderma constituunt, et ut in area pellucida, sic in area opaca adsunt, hac solum intercedente differentia, quod in area pellucida membrana pituitosa longe tenerior est, ac in zona opaca.

Both these membranes constitute the whole blastoderma and are present both in pellucid area and in opaque area, only with the verifying of this difference, since in the pellucid area the pituitous membrane is extremely softer than in the opaque zone.

Oriuntur halones in vitello. Generatim halones audiunt circuli albidi maculae circumducti[11]. Invenimus autem, duas esse distinguendas halonum species; pars enim a blastodermate producitur, cujus limbus pallidior per membranam vitelli translucet, quod non raro interiori etiam gaudet exigua albida zonula.

In the yolk are sprouting some halos. From the point of view of the generation, the halos are considered as white circles surrounded by a stain. Actually I have found that the types of halos have to be separated in two types; in fact a part is produced by the blastoderma, whose paler edge shines through the membrane of the yolk, since not rarely it enjoys also of an internal very small white zone.

Hi [28] halones jam ante incubationem adsunt, et in incubatione cum augmento blastodermatis amplificantur. Alii autem halones duo vel tres prima incubationis die in ipso vitello oriuntur, et sunt circuli plumbeo-albidi, ipsi vitelli massae inhaerentes, et ex ipso vitello per incubationem producti; horum exterior tamen semper limbo blastodermatis respondet. Quanta autem his halonibus insit varietas, Malpighius sufficienter indicavit[12].

These halos are already present before the incubation and during the incubation they magnify with the increase of the blastoderma. But others two or three halos sprout in the yolk itself during the first day of incubation, and they are circles of white leaden colour sticking to the mass itself of the yolk, and are produced through the incubation by starting from the yolk itself; however their more external part is always facing the edge of the blastoderma. Malpighi pointed out in enough way how much variety is present in these halos.

§. 4.
Hora decima sexta.

§ 4
Sixteenth hour

Area pellucida, oblonga, pyriformis 2 ad 3 lineas longa est. In ipsa conspiciuntur duae lineolae obscuriores parallelae, quae a plicis, quas blastoderma versus testam format, proficiscuntur. Haec prima embryonis nascentis vestigia[13] plicae [29] primariae non immerito audiunt, quod [30] autem iis interest, spatium carinatum cum Malpighio nominamus.

The pellucid area is oblong, pear-shaped, long 2-3 lines <- 4,50-6,75 mms>. In it two darker little lines are seen, parallel, starting from the plicae formed by the blastoderma in direction of the shell. Rightly these first vestiges of the bearing embryo are called primary plicae, but what is in the middle of them with Malpighi I call carinate space.

In ea extremitate, quam hae plicae obtusiori areae pellucidae fini obvertunt, mox, post earum ortum, flexione arcuata sese conjungunt; in opposita autem extremitate a se invicem distantes patescunt.

In that extremity these folds are turning toward the more blunt limit of the pellucid area, immediately after their appearance they are joining with an arched bending; but at the opposite extremity they widen, being distant between them.

Dum haec contingunt, area pellucida sensim sensimque suam formam mutat, dilatata; obtusior pars gracilescit et sic figura pyriformis in illam, quam Blumenbach pani saccharato, vulgo Biscuit dicto, recte comparat, mutatur, nobis uno verbo abhinc soleaeformem appellandam.

While these things happen, the pellucid area, dilated, slowly changes its shape; the blunter part grows thinner and so the pear-shaped aspect turns itself in something rightly compared by Johann Friedrich Blumenbach* to the sugared bread, usually called biscuit, that from this moment I have to call with only one word: soleaeformem, sole-shaped.

Inter utramque plicam primitivam, brevi ab eorum ortu et conjunctione intervallo, tenue filamentum albidum nascitur, quod mox medullam spinalem rite agnoscimus.

Among both the primary plicae, in a short interval from their formation and union, a thin white filament is born, that rightly immediately I recognize as spinal marrow.

Versus arcuatam plicarum primitivarum conjunctionem medulla spinalis in capitulum, altero fine autem in rhombum terminatur.

Toward the arched conjunction of the primary plicae, the spinal marrow ends in a little head, but at the other extremity in a rhomb.

Blastodermatis area opaca iterum in duas zonas distinctas divisa est: interna angustior, intensior, flava, rugoso-grumosa, ab exteriori, latiore, aequaliori circulo albido separatur.

In its turn the opaque area of the blastoderma is split into two distinct zones: the inner one, smaller, more strong, yellow, rough and lumpy, is separated from the external one, which is wider, by a more uniform white circle.

[31] Zona interna margine suo interiori areae pellucidae fines describit, figuramque biscuitformem seu soleaeformem pariter exprimit, margine vero exteriori elliptico zonae externae contigua est.

The inner zone by its more internal edge describes the boundaries of the pellucid area, and likewise it reproduces an aspect of biscuit or of sole, but with the elliptic external edge it is adjoining to the external zone.

Halones ampliati.

The halos are bigger.

Nucleus intumescit, a vitello facillime separatur et foveolam superficiei, qua antea cum blastodermate cohaeserat, impressam ostendit.

The nucleus swells out, very easily it separates from the yolk, and shows a small pit imprinted on the surface to which before it had stuck.

§. 5.
Hora vigesima.

§ 5
Twentieth hour

Embryonis ex plicis primariis et medulla spinali consistentis, ex blastodermate nati, soloque natali indisolubili modo adnexi duas distinguimus extremitates, superiorem seu capitalem, ubi plicae coierunt, et inferiorem, seu caudalem, ubi plicae patent.

Of the embryo, constituted by the primary plicae and by the spinal marrow, born from the blastoderma and linked in an indissoluble way to the native support, we distinguish two extremities, the superior or cephalic, where the plicae joined themselves, and the inferior or caudal, where the plicae are evident.

Extremitas capitalis versus ovi interiora paulisper supra medullae spinalis capitellum reflectitur, et sic plicam valde exiguam, transversalem, semilunarem format[14].

The cephalic extremity bends toward the more internal parts of the egg, a little bit above the extremity of the spinal marrow, and so it gives shape to a very small plica, transversal and crescent-shaped.

[32] Haec plica transversalis consistit ex 1) duabus plicis primariis, quae ob necessariam elevationem in angulo flexionis tanquam cornua parva eminent; 2) ex arcu plicarum apices conjungente, qui plicae terminum facit, ex quo complicatum blastoderma iterum reflexum et deplanatum in aream pellucidam continuatur, praeterquam quod apices plicae transversim sibi oppositae [33] ad latera embryonis paulisper incurvatae descendunt versus caudam. 3) Ex membrana spatii carinati utrique plicae interjecta.

This transversal plica consists 1) in two primary plicae, sticking out in the angle of the flexion as small horns because of a necessary elevation; 2) in an arc linking the apexes of the plicae, which determines the end of the plica, from which the folded up blastoderma, newly bent and flattened, continues in the pellucid area, except the fact that the apexes of the plica, opposed to itself transversally and a little bent toward the sides of the embryo, go down toward the tail; 3) in a membrane of the carinate space interposed to both plicae.

Quando per macerationem blastoderma in duas, ex quibus componitur, membranas dividitur, et membrana serosa sub microscopio consideratur; apparet hujus superficiei internae, qua pituitosae incumbit, adhaerens tenue stratum minutissimorum globulorum ubique aequalium, subtransparentium. Hocce stratum globulorum non per totum blastoderma diffunditur, sed tantummodo aream pellucidam et zonam areae opacae interjorem occupat, ita ut ipsa areae opacae in duas zonas divisio (h. 16. non nisi ab hoc strato ordiatur, cujus margo interiorem zonam ab exteriori separat[15]).

When by means of the maceration the blastoderma splits into the two membranes by which it is composed, and the serous membrane is analyzed under the microscope, of this inner surface, by which it leans to that mucous one, a thin adherent layer of dwarfish globules anywhere identical, semitransparent, is seen. This layer of globules doesn't spread through the whole blastoderma, but only occupies the pellucid area and the more inner opaque zone, so as the division itself of the opaque area in two zones (unless at 16th hour it takes start from this layer, whose edge separates the inner zone from the external one).

Memorabilis est hujus strati metamorphosis. Circa horam duodecimam enim [34] non completum stratum, sed dispersi globulorum acervuli tanquam insulae apparent, quae demum in stratum non interruptum confluunt, quod postea denuo in sanguinis insulas et in vasa sanguinea abit, propriae membranae, quam vasculosam dicimus, naturam induens et tertiam eamque mediam blastodermatis lamellam constituens.

The metamorphosis of this layer is worthy of mention. In fact about the 12th hour a complete layer appears, but some scattered dollops of globules appear as being islands finally merging in a continuous layer, subsequently completely turning into islands of blood and in blood vessels, assuming the aspect of the proper membrane we call vascular, and also constituting that third middle lamella of the blastoderma.

§. 6.
Hora vigesima quarta.

§ 6
Twenty forth hour

Ad latera embryonis plicis primitivis quasi appensa oriuntur vertebrarum rudimenta[16], maculae forma fere quadrata, colore subflavo, albicantibus intervallis separatae et in duas lineas parallelas dispositae.

At the sides of the embryo, almost suspended at the primitive plicae, the sketches of the vertebrae are originated, spots of almost square shape, of yellowish colour, separated by white intervals and placed along two parallel lines.

Plicae primitivae antea rectae serpentine flectuntur[17], et quasi undulosae fiunt, unde spatium carinatum in seriem cellularum dividitur. Versus finem caudalem plicae a se invicem divergentes [35] discedunt, et circa rhombum medullae spinalis imperfectum arcum formant.

The primitive plicae, at first straight, are bending like a snake and become almost undulant, so the careened space is divided in a series of little cells. The among them divergent plicae are separating toward the caudal extremity and form a defective arc around the rhombus of the spinal marrow.

Halones ampliati sunt, et latiores facti se hinc inde attingunt, undulati quid ostendentes.

The halos became larger and, grown larger, are touching themselves from one side to the other, showing something undulated.

§. 7.
Hora trigesima.

§ 7
Thirtieth hour

Plicae primitivae, quae prius patentes medullam spinalem inter se excipiebant, jam versus se invicem inclinantur, praecipue in media caput inter et caudam regione. Dum haec inclinatio fit, margines plicarum sibi admoventur, medulla spinalis tegitur, qua contecta demum concrescunt. Sed cum haec inclinatio, marginum appropinquatio, eorumque concretio non nisi in medio contingant, eaedem, de quibus diximus plicae, ubi ad dilatationem rhomboideam medullae spinalis accedunt, diversi persistunt, ad extremitatem capitalem autem, serpentinam flexionem conservant et seriem trium vel quatuor cellularum magnitudinis progressive adauctae efficiunt[18].

The primitive folds that before, open, welcomed the bone marrow among them, now are inclined towards each other, especially in the region that is located in the middle between the head and the tail. While this inclination happens, the edges of the plicae move towards each other, the spinal marrow covers itself, and after it is covered they finally stiffen. But while this inclination, the approaching of the edges and their stiffening are happening only in the center, the same plicae of which we have spoken, when are approaching to the rhomboid expansion of the spinal marrow, remain different; actually toward the extremity of the head they keep a serpentine flexion and create a series with the size of three or four cells progressively increased.

[36] Plica transversalis sensim dilatata et prolongata versus extremitatem caudalem descendit, et vaginam capitis, Wolffio dictam, format. Considerandum nempe est, re vera duas adesse plicas transversales, primam sive superiorem, quae e reflexione corpusculi embryonis oritur, et secundam sive inferiorem, quam reflexio blastodermatis in planitiem redeuntis efficit, et supra quam prima prominet. Quod jam ad superiorem plicam spectat, haec ipsa ad constituendum corpus embryonis confert; secunda autem sive inferior, si embryonem, cum blastodermate ex ovo {exemtum} <exemptum>, dorso imponas, et superficiem internam sive abdominalem spectes, primam tegit, et hoc tegmen proprie est, quod evolutione elongetur.

The transversal plica, slowly dilated and lengthened, goes down towards the caudal extremity and forms the sheath of the head, as Kaspar Wolff calls it. Actually we have to consider that truly there are two transversal plicae, the first one or superior that is born from the refolding of the corpuscle of the embryo, and the second one or inferior that determines the refolding of the blastoderma that becomes again to be flat, and above which the first one is sticking out. What now is turned toward the superior plica, this one itself contributes to the formation of the embryo's body; but the second or inferior one, if you put the embryo on its back with the blastoderma removed from the egg and you look at the inner or abdominal surface, it covers the first, and this coverage is placed in an appropriate way, since it would be removed by the evolution.

Cor sub vagina capitis tanquam oblongus sacculus nondum certis descriptus limitibus apparet.

The heart is visible under the sheath of the head as an oblong bag not yet delineated by secure boundaries.

Stratum globulosum, membranae serosae adhaerens, retis speciem prae se fert; per globulos nempe lineolae perlucidae sibi intertextae serpunt.

The globular layer, adherent to the serous membrane, shows the aspect of a net; actually through the globules are winding some little transparent interwoven lines.

Diameter blastodermatis sex vel octo linearum.

The diameter of the blastoderma is of 6 or 8 lines.

Halones fere evanuerunt; nucleus auctus.

The halos have almost disappeared; the nucleus is increased.

[37] §. 8.
Hora trigesima sexta.

§ 8
Thirty sixth hour

Cornua plicarum primitivarum, quae, ubi plica transversalis fit, prominent[19], ad se proxime accedunt[20] et dum concrescunt, spatium orbiculare includunt, unde frons et facies pulli oriuntur. Ad utrumque hujus orbiculi latus duo alia spatia orbicularia nascuntur, paulisper retro posita, prima oculorum rudimenta[21], quae ab initio modo dilatationes laterales primi intermedii orbiculi esse videntur.

The horns of the primitive plicae, which, when a plica becomes transversal, are sticking out, get closer to each other and while growing together they contain a circular space, whence the forehead and the face of the chick are born. In proximity of both sides of this circle two other circular spaces are born, a little bit placed behind, the first sketches of the eyes, initially seeming to be only lateral dilatations of the first central circle.

Cor angustius factum est, canalis cylindricus, rectus, in regione cardiaca Wolffii situs, ad caput adscendens. Stratum globulorum in distinctas insulas solutum; ipsae insulae colorem subflavum assumunt; globuli autem annulum terminalem constituentes rubedine inficiuntur.

The heart became smaller, the cylindrical channel, straight, located in the cardiac region of Kaspar Wolff, rises toward the head. The layer of the globules is dissolved in separate islands; the islands themselves assume a yellowish colour; but the globules constituting the terminal ring are dyed of red.

[38] §. 9<.>
Hora quadragesima secunda.

§ 9
Forty second hour

Extrema capitis pars, siquidem superiorem ad albumen spectantem superficiem consideremus, quae blastodermati prius incubuit et ab illo superne acus ope sublevari potuerat, nunc parvae foveolae immersa est, quam blastodermatis superior, ultra caput prominens pars efficit, ita ut caput ex hac foveola eximere possis. Plica, hujus foveolae marginem constituens, inchoamentum est amnii.[22]

The extreme part of the head, if we consider the upper surface turned toward the albumen, that initially was leant on the blastoderma, and that had been possible to be lifted by a needle from its superior part, now is immersed in a little dimple created by a superior part of the blastoderma sticking out beyond the head, in such a way that it is possible for you to remove the head from this dimple. The plica constituting the edge of this dimple is the sketch of the amnion.

Cor in latus sinistrum arcuatur et duabus stricturis in tres vesiculas, imperfecte tamen, dividitur, et in extremitate inferiori, quasi bifidum in crura maxime divergentia desinit<.>

The heart bends like an arc toward the left side and through two narrowing splits into three vesicles, however in a defective way, and at the inferior extremity, almost bifid, ends in extremely divergent legs.

Vagina capitis usque ad cordis in duo crura divisionem porrecta est, et in hac regione foveam cardiacam, quae retro cor in oesophagum ducit, format; anguli autem laterales hujus vaginae valde prominent, versus caudam tendentes.

The sheath of the head lengthens up to the division of the heart in two legs, and in this region it forms the cardiac pit that behind the heart brings in the oesophagus; but the lateral angles of this sheath are quite a lot sticking out by going toward the tail.

Ad inferiorem foetus apicem nunc invenimus circumflexam blastodermatis partem, quae dum postea futuram caudae vaginam efficit, apud Wolffium involucrum [39] caudae audit, cujus margines ad embryonis latera adscendunt et innatas a fovea cardiaca plicas transeunt.

Toward the inferior apex of the fetus we now find the circumflex part of the blastoderma, that, while subsequently is constituting the future sheath of the tail, in Kaspar Wolff is said wrap of the tail, whose edges go up to the sides of the embryo and overcome the plicae originating from the cardiac pit.

Insulae rubent, et prolongatae in rete confluunt.

The islands are red, and lengthened they converge in the net.

Membrana vitelli, ubi blastoderma tegit, tenuissima facta est.

The membrane of the yolk, whereas covers the blastoderma, became very thin.

Albumen supra formatum blastoderma plane recedit, et huic liberum accessum ad internam testae superficiem dat.

The above formed albumen goes wholly away from the blastoderma and gives it a free access to the inside surface of the shell.

§. 10.
Hora quadragesima octava.

§ 10
Forty eighth hour

Margines foveolae, in qua libera superior pulli pars collocatur, ita increverunt, ut sub forma vaginae semilunari margine terminatae eam partem a dorso obtegant.

The borders of the dimple, where the free superior part of the chick is placing itself, are so increased to cover that part protecting it from the back as a sheath delimited by a semi lunar edge.

Foetus ex recto suo situ paullulum superiore parte ad sinistrum latus conversus et ab extremo capitis incurvatus est, ita ut regiones sincipitis[23] et occipitis jam manifestentur.

The fetus with the superior part is slightly turned from its straight side toward the left side and is bent starting from the extremity of the head, so that the regions of sinciput and occiput are already showing themselves.

Quod hucusque stratum globulosum diximus, in membranam vasculosam, inter duas blastodermatis laminas interpositam transmutatur. Sanguinis nempe insulae, in rivulos contractae, parietes induunt, et hac ratione vasa sanguifera formant, quae [40] iterum tenui lamina connectuntur; quare blastoderma jam e tribus componitur stratis.

That we till now have called globular layer, turns itself into the vascular membrane interposed among two laminae of the blastoderma. The blood's islands, precisely, gathered in rivulets, become covered with walls, and in this way they form the blood vessels, newly joined by a thin lamina; that's why the blastoderma is now composed by three layers.

Cellulae, quas distantes et flexuose incedentes plicae primitivae in regione capitali formant, replentur vesiculis, continuam sed subdivisam cavitatem constituentibus, in quibus cerebrum oritur, et in posteriori quidem eaque magis in longitudinem protracta, medulla oblongata, in secunda globosa corpora quadrigemina, in tertia minori et angustiori crura cerebri et thalami nervi optici et in anteriori quarta iterum majori, hemisphaeria.

The cells, formed distant and endowed with supple movement in the cephalic region by the primitive plicae, are filling with vesicles constituting a continuous but subdivided cavity, in which the brain is born, and the medulla oblongata in the posterior and longer one, in the second cavity the globular quadrigeminal bodies, in the smaller and narrower third the legs of the brain and of the thalamus of optic nerve, and the hemispheres in the newly greater fourth anterior cavity.

In inferiori, vitello nempe obversa blastodermatis superficie, binae ad utrumque latus pulli, ubi jam abdomen inspicis, decurrunt plicae, duae externae, alterae duae internae. Plicae externae ex omnibus blastodermatis stratis simul {sumtis} <sumptis>, internae vero ex strato vasculoso et pituitoso sine strato seroso formantur[24].

In the inferior cavity, naturally after having turned the surface of the blastoderma toward the yolk, two plicae are running near both sides of the chick, there where you already see the abdomen, two external and the other two internal. The external plicae are formed by all the layers of the blastoderma put together, while the internal ones are formed by the vascular and mucous layer without the serous layer.

[41] Exteriores plicae abdominis, quod omnino patet, margines constituunt, sed cum [42] postea partim intestinorum formationi, nempe stratis pituitoso et vasculoso, [43] inserviant, partim, nempe strato seroso, abdominis parietes constituant, illas plicas [44] intestinales, has plicas abdominales vocamus.

The external plicae of the abdomen, being a thing entirely evident, constitute some margins, but since subsequently they are partly available for the formation of the bowels, that is with the mucous and vascular layers, partly, that is with the serous layer, they constitute the walls of the abdomen; those we call intestinal plicae, these we call abdominal plicae.

[45] Plicae interiores autem, quae coeundo mesenterium formant, mesentericae dicendae sunt.

But the more internal plicae, which, joining themselves, make the mesentery, must be called mesenteric plicae.

Fovea cardiaca amplam cavitatem et verum orificium apertum, in supremam ventriculi patentis partem transiens, refert: figura ovalis fere est, superne rotunda et latior, unde plicae intestinales, deorsim vero sensim angustior, unde plicae mesentericae ad utrumque latus foetus descendunt et in involucri caudae inferiorem partem desinunt.

The cardiac fossa shows a wide cavity and a true open orifice going in the higher part of the visible ventricle: the shape is almost oval, upward round and wider, whence the intestinal plicae go down, but a little more narrow downward, whence the mesenteric plicae go down at both sides of the fetus and finish in the inferior part of the wrap of the tail.

Parietes vaginae caudae inter se magis approximatae, vagina ipsa magis in longitudinem protracta, primordium intestini recti exhibent.

The walls of the wrap of the tail more close each other, the wrap itself more extended in length, are showing the sketch of the rectum.

Denique renes quoque plicis mesenterii adhaerent, quibus igitur, ut Wolffius commemorat, non solum mesenterii, sed renum quoque primordium repraesentatur.

Finally also the kidneys stick to the mesenteric plicae, by which therefore, as Kaspar Wolff remembers, not only the sketch of the mesentery is shaped, but also of the kidneys.

Cor curvum canalem figurae ferri equini seu parabolae refert, et in sinistram foetus latus flexum prominet[25].

The heart reminds a bent channel with the appearance of a horseshoe or of a parable, and leftwards the flex side of the fetus is sticking out.