Secundo itaque ab incubatu die, luteum observavi deferri ad cacumen, aliquo pacto alteratum, et in medio quasi subalbidum: cuius rei in primis Aristoteles non meminit. In aliqua vero parte albuminis, quae pariter erat alterata, semen Galli apparebat, quod tres illas videbatur obtinere qualitates, quales iam ante diximus.

- Chicken embryo - On the second day of incubation I observed that the yolk was moving to the sharper end of the egg, and it was altered in some way and almost whitish in the middle: a thing not mentioned first of all by Aristotle. In some part of the albumen, which was equally altered, there appeared the rooster’s semen, since it showed to have those three characteristics which I have already described before.

Tertia die ablato putamine in parte ovi obtusa, vidi albumen, et reliquam substantiae ovi partem in superiori putamine separatam. Recesserat autem albumen aliquantulum a putamine, quemadmodum fieri videmus in ovis omnibus, quae minus recentia sunt. Hinc Plinius[1] ova schista appellat tota lutea, quae triduo incubatu tolluntur. Vocat autem schista, teste Hermolao, quia dividantur, et discedat vitellus a candido.

On the third day, after the shell was removed in the blunt part of the egg, I saw the albumen and the remaining part of egg’s substance displaced towards the upper shell. For the albumen had receded a bit from the shell, as we see also to happen in all eggs which are less recent. Hence Pliny calls schista – split - eggs those which are entirely yellow and are removed at the third day of incubation. According to Hermolaus Barbarus, he calls them schista  - split - because they split and the yolk separates itself from white.

Videbam item manifeste admodum membranas illas tres, quas ovis inesse ex Alberto dixi, et ex Aristotele etiam colligitur: neque verum est, quod secunda earum sit recenter genita. Si enim illud ita esset, minime in ovis nondum incubatis conspiceretur. Inest autem et his, ut etiam vidi, sed albior in incubatis caloris causa. Eadem die vitellus videbatur versus ovi partem acutam: atque hoc est, quod dicebat Philosophus[2]. Effertur per id tempus luteus humor ad cacumen, ubi est ovi principium, nam ibi est maior calor, et vis spermatis. Apparebat etiam in albumine exiguum velut punctum saliens, estque illud quod Philosophus cor statuit. Ex eo vero evidenter admodum videbam enasci venae trunculum, et ab hoc duos alios ramulos proficisci, qui meatus illi fuerint sanguiferi, quos ad utranque tunicam ambientem vitellum, et albumen protendi ille dixerat. Sum autem omnino eius sententiae, ut eiusmodi vias credam esse venosas, ac pulsatiles, sanguinemque in iis contineri puriorem, principalium membrorum generationi, iecoris nempe, et pulmonis, similiumque idoneum: adeo ut recte dixerit Philosophus[3], tertia die signa apparere, an ova foecunda sint futura: licet eiusmodi observatio in maiorum avium, utpote Cycnorum, Anserum, ac id genus aliarum ovis locum minime habeat. In eiusmodi enim, ut idem Philosophus testis est, paulo tardius ea signa apparent.

And so as well I saw quite clearly those three membranes situated inside the eggs, as I said when quoting Albertus and as it is possible to catch also from Aristotle: and it is not true that the second membrane is recently generated. For if this were so, it would by no means be visible in eggs not yet incubated. On the other hand it is present in these eggs, as I also saw, but is more white in incubated eggs because of heat. On the same day the yolk was towards the sharper end of the egg: and this is what the Philosopher said. During this time the yellow liquid moves to the pointed part where the principle of the egg is located, for the heat is greater there as well as the force of the sperm. It was also visible in the albumen something like a small jumping speck, and this is what the Philosopher established as the heart. Truly, I saw quite clearly arising from it the little trunk of the vein, and from this two other branches coming forth, which would have been those blood-ducts which he said to go towards the two tunics surrounding the yolk and the albumen. In fact I am entirely of Aristotle’s opinion, since I believe that such ducts are venous, and pulsating, and that the blood they contain is purer, suitable for generation of main organs, particularly of liver and lungs, and similar structures: so much so that the Philosopher rightly said that on the third day there appear the signs whether the eggs will be fertile: although there is very little room for such an observation in eggs of larger birds as swans, geese and other similar fowls. For, as also the Philosopher testifies, these signs appear a little later in such birds.

Quarta die bina videbantur puncta, et quodlibet eorum sese movebat: quae haud dubio cor, et iecur fuerint, quae viscera in ovis triduo incubatis idem dixit. Apparebant item duo alia puncta nigricantia, nempe oculi: et iam luteum manifeste ad acutam ovi partem, ubi maior calor est, et spermatis vis sese receperat. Trahitur autem a spermate illud pro carnis generatione, ut in omnibus animantibus fit, quae sibi simile generant.

On the fourth day two points were visible and each of them moved: without doubt they were the heart and the liver, viscera he said to be present in eggs incubated for three days. There also were visible two other blackish specks, precisely the eyes: and now the yolk clearly withdrew towards the pointed pole where the heat is greater as well as the force of the sperm. For it is attracted by the sperm for the generation of the flesh, as it happens in all living creatures which generate a creature looking like themselves.

Quinta die non amplius punctum illud quod cor esse diximus, extra videbatur moveri, sed obtegi, ac cooperiri, et duo illi meatus venosi evidentiores conspiciebantur, alter vero maior altero: nec verum est, quod Albertus scripsit, apparere in tunica illa, quae albumen includit: nisi forte id de tertia tunica, seu secundina dixerit, cui evidenter venae insunt, nam alioqui in illa nullius venae vestigium inerat. Harum venarum insita vi reliqua albuminis portio quasi in palearem colorem immutatur. Videbantur etiam ramuli ad locum tendere, in quo caput formatur, eo scilicet puriorem materiam, a qua caput, ac in eo cerebrum fiat, una cum virtute formatrice deferentes. Erat autem capitis fabrica valde rudis adhuc ac informis: oculi vero conspectiores, atque ervi quasi magnitudine.

On the fifth day that speck which I said was the heart did not seem to move more, but that it was hidden and covered up, and those two vein-ducts were more evident, one larger than the other: and it is not true what Albertus wrote, that they appear in that tunic which encloses the albumen: unless perhaps he was alluding to the third tunic - allantoid, or afterbirth, in which there are clearly visible veins, for however there was no trace of a vein in that enveloping the albumen. By the inborn force of these veins the remaining portion of the albumen changes to a sort of straw color. Little branches seemed to tend to the place in which the head is formed, carrying to it, along with the molding force, a purer material from which the head is formed and, within it, the brain. The sketch of the head was still quite rough and shapeless: the eyes, to say the truth, were more visible and nearly of the size of a lentil.

Sequenti dein die ablato superiori partis obtusae putamine, eiectisque duabus prioribus tunicis, tertia evidenter cernebatur venulis referta: de hac locutum fuisse Philosophum[4] arbitror cum inquit: Membrana etiam fibris distincta sanguineis: atque haec meo iudicio secundina dici potest. Dein inter hanc, et quartam membranam, quae foetum involvebat, humor erat aquosus: quem autumo serosam albuminis partem esse, quae post natum foetum superest, tanquam ad generationem inepta. Eam vero membranam innuere videtur Aristoteles a meatibus illis venarum ortum ducere, quatenus scilicet vi fibrarum a venoso illo meatu ortarum in palearem, vel sanguineum colorem immutatur. Cernebatur deinde totus foetus moveri, et oculi iam maiores erant, quam in praeterita die: at partes inferiores, thorax nempe, venter, et pedes, erant valde imperfectae, nec discerni adhuc poterant, et rostrum erat muccosum: ut recte dixerit Aristoteles[5]: pars inferior corporis nullo membro, a superiori distingui inter initia cernitur. Caput denique tota inferiori corporis parte maius erat.

Then on the following day - the sixth - when the upper part of the blunt end of the shell was removed, and the two first tunics were taken away, the third tunic covered by little veins was clearly visible: I think the Philosopher spoke of this one when he said: Also a membrane marked with bloody fibers, and this in my opinion can be called afterbirth. Then between this tunic and the fourth, which enveloped the foetus, there was a watery liquid: which I believe is the serous part of the albumen, which is left over after the foetus is born, being unfit for generation. Aristotle seems to hint that this membrane takes its origin from those vein-ducts since by the force of the fibers arising from that vein-duct it is changed to a straw or bloody color. Moreover the entire foetus was seen to move and the eyes were by now larger than on the day before: but the lower parts, and precisely thorax, belly and legs were quite imperfect, neither they could yet be discerned, and the beak was mucous: as Aristotle rightly said: at the beginning the lower part of the body cannot be distinguished from the upper part through any organ. Finally, the head was larger than the entire lower part of the body.

Septima die aperta quarta tunica foetum conspeximus parvum adhuc, ac indistinctum cum oculis tamen magnis, triplicique in illis humore, crystallino nempe, vitreo, et aqueo. Aperto capite iam cerebrum aperte cernebatur, minus vero reliquae partes. Unde dicebat Philosophus[6]. Paulo post (intelligit meo iudicio diem quintam usque ad nonam inclusive) et corpus iam pulli discernitur, exiguum admodum primum, et candidum, conspicuum capite, et maxime oculis inflatis, quibus ita permanet diu, {uti nos conspeximus:} <uti nos conspeximus:> et sero, inquit, [218] decrescunt oculi, et se ad ratam proportionem contrahunt; quod quidem verissimum est: siquidem in quartadecima, aut quintadecima die aliquantum resident diminuti propter caloris digestionem.

On the seventh day, when the fourth tunic – amnios - was opened, I saw the foetus still small and indistinct, with eyes nevertheless large and a triple humor in them, and precisely crystalline, vitreous, and aqueous. After the head was opened the brain was by now clearly visible, but less the remaining parts. Hence the Philosopher was saying: A little later (he means, in my judgment, the fifth to the ninth day inclusive) the body of the chick is now visible, quite small at first and snow-white, conspicuous with its head and great bulging eyes which remain a long time thus, as I saw: later on, he says, the eyes decrease in size and contract to their proper volume; this is quite true: in fact, on the fourteenth or fifteenth day they turn out fairly diminished because of the concoction by the heat.