Octava rursus die oculi maiores adhuc videbantur, utpote ciceris ferme magnitudine. Totum corpus tunc sese velociter movebat, et iam crura, et alae distincte cerni incipiebant. Rostrum tamen interim muccosum adhuc erat. Sed forte quispiam quaerat, cur prius superiores, quam inferiores partes in eiusmodi formatione appareant: cui responsum velim, virtutem, seu facultatem formatricem in superioribus magis quam in inferioribus vigere, quod spiritales sint, et per consequens plus caloris obtineant. Caeterum istaec omnia, quae hac die videbam, sequenti manifestiora apparebant.

- Chicken embryo - Furthermore, on the eighth day the eyes appeared further larger, being that almost had the size of a chickpea. The entire body then moved swiftly and by now legs and wings began to be distinctly visible. Nevertheless the beak was meanwhile still of mucous texture. Perhaps someone might ask why in a formation of this sort the upper parts appear before the lower parts: I would like to reply to him that the formative force or faculty is stronger in the upper parts rather than in the lower ones, since the former are respiratory and consequently have more heat. Furthermore, all the things I saw on this day became clearer on the following day.

Decima die non amplius caput toto corpore maius erat, magnum tamen, ut in infantibus etiam videmus: magnitudinis autem causa est humidissima cerebri constitutio. Quod vero Aristoteles dicit[1] oculos fabis maiores esse, id profecto minime verum est, si de vulgaribus nostris fabis locutus fuerit, cum alioqui ervi, vel ciceris albi magnitudinem non excederent: atque hinc etiam non absurde quispiam colligat fabas antiquorum fuisse rotundas, quales araci sunt, quem ideo fabam veterum quidam existimant. Neque etiam verum est quod tradit[2], {tunc}, <tunc>, scilicet, oculos pupillis adhuc carere. Etenim hae non tantum hac die apparebant, sed duabus etiam praecedentibus, una cum omnibus partibus, ac humoribus. Quod vero ait detracta cute nihil solidi videri, sed humorem tantum candidum, rigidum, et refulgentem ad lucem, nec quicquam aliud, id de crystallino humore mihi dixisse videtur, qui tamen haud solus apparebat, sed vitreus quoque et albugineus, unde non parum hallucinatus videri potest Philosophus, uti etiam Albertus, qui eo tempore nihil duri, et glandulosi in iis reperiri existimat, cum crystallinus humor solidus sit, ac quam maxime conspicuus.

On the tenth day the head was no longer larger than the entire body, but it was large nevertheless, as we also see in newborn children: the reason for its bigness is the very humid constitution of the brain. As to the fact that Aristotle says the eyes are larger than broad-beans, this is by no means true if he has spoken of our common broad-beans since generally they do not exceed a lentil or a white chickpea in size: and hence someone doesn’t deduce absurdly that broad-beans of the ancients were round like wild peas - Pisum arvense - are, whence some people think they are the broad-bean of the ancients. Nor is it true what he reports, that at that time the eyes still lack pupils. For not only did they appear on this day but also on the two previous days along with all their parts and humors. When he said nothing solid could be seen when the covering is removed but a snow-white humor, stiff and shining in the light, and nothing else, he seems to me to have said this of the crystalline humor, which, however, did not appear alone, but also the vitreous and albugineous - sclera, hence the Philosopher seems to have got the wrong end of the stick, as Albertus did also, who thinks that at this time there is nothing hard and glandulous, whereas the crystalline humor is solid and very well visible.

Eadem item die vidi omnia viscera, nempe cor, iecur, pulmonem. Cor autem, et iecur erant albicantis coloris: et cordis motus non solum apparebat, antequam foetum aperirem, sed iam secto etiam thorace moveri videbatur. Erat autem pullus involutus quartae illi membranae plurimis venis refertae[3], ne in humore iaceret. Cernebam etiam vasa umbilicalia prope anum ad umbilicum deferri, ibique infer<r>i, ut cibum per illum petat foetus. Vidi denique, quod Aristoteles non advertit, in dorso prope uropygium pennarum principia nigricantia menti humani cuti non absimilia, cui pili abrasi sint.

On the same day I saw all the viscera, that is, heart, liver, lung. The heart and liver were of a whitish color: and the heart’s movement not only was evident before I opened the foetus but it seemed to move even when the thorax had been cut. The chick was wrapped up in that fourth membrane – amnios - filled with many veins so that it would not become immersed in the liquid. I also saw the umbilical vasa near the anus going towards the umbilicus and entering there, so that the foetus might take its food through it. Finally, I saw something Aristotle does not mention: on the back near the uropygial gland the blackish beginnings of the feathers, very similar to the skin of the human chin when its bristles have been shaved off.

Die subsequenti haec omnia erant manifestiora, et in superioris rostelli extremitate erat quid albidi, cartilagineum, et subduriusculum, quod rursus die decimatertia magis erat conspicuum. Erat autem rotundum milii grano haud absimile. Sagacissima rerum parens natura id ibi fabricasse videtur, ut impediat, ne rostello suo vel venulas, vel membranulas, vel alias quascunque tenerrimas particulas pertundat. Aiunt mulierculae, pullos iam natos cibum capere non posse nisi prius id auferatur.

On the following day all these items were more evident, and on the extremity of the upper beak there was something whitish, cartilaginous and rather hard which afterwards, on the 13^th day, was more apparent – the diamond. It was round, not dissimilar to a grain of millet. Nature, very shrewd parent of the things, seems to have built this here to prevent that with its little beak he bruises or little veins, or little membranes, or any other quite tender part. Farm women say that new-born chicks cannot take food unless this structure is first removed.

Decimaquarta die pullus iam totus plumescebat. Decimaquinta in digitis ungues albicantes apparebant. Die vero decimasexta ovum aperire placuit in opposita parte, ubi nativa tunica, sed unica tantummodo apparebat, eaque alba. Alteram enim quam in altera parte semper videram, hic observare minime datum est. Itaque dubitabam an ea tantum pro albuminis tutela nata sit, cum scilicet ovum non sit recens, vel ad pulli defensionem in ovo incubato. Nam indies illa magis magisque decidere videtur, et foetum sequi, qui sui gravitate deorsum decidit.

On the fourteenth day the chick was already entirely covered with down. On the fifteenth, whitish nails appeared on its toes. On the sixteenth day I want to open the egg in the opposite part where was visible the tunic belonging to the shell, but only one, and it was white too. For the other one I ever had seen in the opposite side, in this point it is quite impossible to be observed. Thus I was doubtful whether it took birth only for the protection of the albumen when the egg is not recent or for the defense of the chick in the incubated egg. For day by day this tunic seems to fall down more and more and to follow the foetus, which falls downward because of its own weight.

Aristoteles etiam unicam tantum esse eiusmodi tunicam his verbis[4] videtur innuere. Sunt, inquit, quandoque locata ova hoc ordine, prima, postremaque ad testam ovi membrana posita est, non testa ipsius nativa, sed altera illi subiecta: liquor in ea candidus est, quasi diceret, omnes partes in ovo locatae sunt hoc ordine; nempe prima, postremaque ad testam ovi membrana posita est. Intelligit meo iudicio per primam, et postremam membranam, eas membra<na>s recens in incubato ovo genitas, eas videlicet, quas aliquoties appellavi tertiam secundinam, et quartam, quam involventem foetum dixi. Nam cum dicit testae nativam non esse, ostendit nec primam, nec secundam esse, quae ab altera ovi parte reperitur. Videtur igitur excludere hanc nativam sive primam, vel secundam, et intelligere tertiam, quam secundinam saepe vocavi. Cum vero dicit[5], sed altera illi subiecta, intelligit eandem, secundinam nempe testae subiectam, quod vel ex hoc maxime liquet, quod candidum in ea liquorem inesse dicat. Is enim, ut supra ostendi, inter tertiam, et quartam continetur. Hinc manifesto errore Suessanus convincitur, qui ex Ephesio per primam interpretatur eam, quae testae adhaeret, per postremam vero, quae albumini.

Also Aristotle by the following words seems to hint that such a tunic is only one. He says: Since the eggs are set up in this order, set against the eggshell there are a first and a second membrane, the latter not being that belonging to the shell, but being the other lying beneath the first one: there is a snow-white liquid in it, as if he was saying that in egg all parts are arranged in this order; and precisely that the first and the second membrane are set against the eggshell. He means, according to my judgment, by first and last membrane those membranes recently generated in the incubated egg, of course those which I sometimes called the third placental one – allantoid - and the fourth which I said is enveloping the foetus - amnios. For when he says that the membrane is not belonging to the shell he shows that it is neither the first, nor the second which is found in the other side of the egg. He therefore seems to exclude that this one belonging to the shell is the first or the second, and to understand that it is the third, which often I called afterbirth. For when he says, but the other lying beneath it, he means that same membrane, that is the afterbirth one, set against the shell, and this is very clear also from the fact that he says there is a snow-white liquid in it. For this liquid, as I showed above, is contained between the third and fourth ones. Hence the Suessanus - Agostino Nifo - proves to be in manifest error for he interprets from Michael of Ephesus as first membrane that which adheres to the shell and as last that which adheres to the albumen.

Quae omnia a nobis observata quotidie in sequentibus diebus evidentiora, utpote in perfectissimo pullo apparebant. Die vero vigesima pullus putamine a parente Gallina ablato hora vigesimasecunda sua sponte exivit. Sequens icon ostendit situm perfecti iam pulli in utero [ovo?[6]].

All these things I daily observed became more evident in the following days, since they were appearing in a quite perfected chick. On the twentieth day, the shell being removed by mother hen, on the twenty-second hour the chick came out by himself. The following picture shows the position of a by now completed chick in the uterus.