[282] EXERCITATIO VIGESIMAQUARTA.
De ovis gemellificis.

24th exercise
The twin eggs

GEMELLIFICA ova sunt, e quibus gemelli prodeunt pulli; eaque, ait Aristoteles[1], binis vitellis praedita sunt; qui in aliquibus tenui albuminis dissepimento separantur, quo minus inter se confusi sint: in aliis nullum est, sed se mutuo contingunt.

The twin eggs* are those whence twin chicks go out, and Aristotle says that «they are endowed with two yolks which in some eggs are separated by a thin layer of albumen so that they are less mixed each other, in other eggs there is no layer of albumen but they are touching each other.»

Vidi saepe ova gemellifica, quorum singulos vitellos bina albumina ambiebant, cum membranis communibus, propriisque singillatim obvolventibus. Alia quoque ova vidimus cum binis vitellis quasi connascentibus, quibus utrisque unicum albumen commune circumfundebatur.

I have frequently seen some twin eggs whose single yolks were surrounded by one own albumen, with common and own membranes surrounding each formation. I have also seen other eggs with two yolks as if they were united each other since the birth, around which only one albumen in common was present.

Gallinae nonnullae sunt, inquit Aristoteles[2], quae omnia gemellifera pariunt; in quibus, quod evenire vitello diximus, perspectum est. Quaedam enim duodeviginti cum peperisset, exclusit geminos; nisi quae irrita fuerunt. Verum ita fit, ut ex gemellis, alter maior sit, alter minor; postremus autem etiam monstruosus.

Aristotle says: «There are some hens laying all twin eggs, in which it has been investigated what we said is happening to the yolk. In fact a hen, having laid 18 of them, gave birth to twins, except those being sterile. Really it happens that one of the twins is greater, the other is smaller, and this last is also monstrous.»

Apud nos interdum gemellifica ova nascuntur, et gemelli quoque aliquando, licet rarissime excluduntur. Ipsemet autem ambos eiusmodi foetus vivos nunquam vidi; quod vel in ovo ipso, vel in exclusione alter pereat. Idque etiam mihi ex Aristotelis verbis fit verisimile, dum alterum maiorem, alterum minorem ait: illum nempe robustiorem, et aetate provectiorem; hunc autem imbecilliorem, magisque ad exitum imparatum; siquidem, ut opinor, bini isti vitelli [283] disparis ortus et maturitatis sunt. Fieri itaque vix potest, quin robustior, et exclusioni iam paratior, si ovum aperiat, ipseque prodeat in lucem, alteri abortum afferat. Si autem ille ovum non ruperit, praesens ipsi periculum (ob defectum aeris) imminet. Adeo alterutri saltem, in exclusione, si non utrique, certa mors impendet.

Sometimes among us some twin eggs are born and sometimes also some twins are born, even if very seldom. But I myself never have seen both such fetuses living, since one of them dies either inside the egg or when hatching. And this is likely to me also according to the words of Aristotle when he says that one is greater and the other is smaller: the first is just more robust and more advanced in age, while the second is more weak and more unprepared to go out, since in my opinion these two yolks are different as far as birth and maturity is concerning. Therefore it can hardly happen that the more robust and more ready to hatch, if it opens the egg and reaches the light, is bringing the abortion to the other. In fact if the first one won't have broken the egg, an immediate danger is impending over it (for lack of air). So that during the hatching at least over one of the two, if not over both, a sure death impends.

Fabricius[3] ista Aristotelis verba vel non videns, vel negligens, ait: Quod si interdum ovum duos obtinens vitellos, intra se pullum cum quatuor cruribus, vel alis, duobusque capitibus, et id genus monstra pariat; nunquam tamen duo invicem separati (ut duo dici possint) pulli sunt: sed unus duntaxat corporis truncus est, qui duo capita, quatuor crura, aliaque huiusmodi annexa habet.

Fabrizi, either not seeing or neglecting these words of Aristotle, says: «Because, if sometimes an egg with two yolks produces inside of itself a chick with four legs or wings and two heads and such monsters, nevertheless they never are two chicks separated from each other (so to be considered two), but only a trunk of the body exists bringing attached two heads, four legs and other such things.»

Unde constat, eum nunquam vidisse, aut ab expertis audivisse, eiusmodi ova binos pullos parere: ac proinde una mecum credere talia ova raro contingere; neque unquam excludere binos foetus vitales.

Thence it results that never he saw or heard from experienced people that such eggs produce two chicks, and therefore to believe with me that such eggs rarely occur and that never give birth to vital fetuses.

Miror autem (visa hac Aristotelis auctoritate) eum dicere, duos invicem distinctos pullos ex ovis eiusmodi nunquam provenire: sed monstrum semper produci. Praesertim cum ipsemet credat foetum e chalazis, tanquam, e materia fabricari; et in gemellifico ovo quatuor chalazas non videre non potuerit.

Actually I marvel (keeping in mind this authority of Aristotle) that he says «never from such eggs two chicks are hatching separated from each other», but a monster is always occurring. Above all since he himself believes that the fetus is made by the chalazae as if being matter, and in the twin egg he had not been able not to see four chalazae.

Crediderim potius, cum in ovo gemellifico duo vitelli eodem albumine concluduntur, invicemque adeo coniuncti sunt, ut eorum cicatriculae, dum simul aperiuntur, unum oculum (colliquamentum a nobis dictum) constituant; monstrosum foetum procreari posse, cum quatuor pedibus, duobus capitibus, et caetera: quippe nihil video, quod impediat: talemque ex ovo Fabricii prognatum arbitror.

Since in a twin egg the two yolks are surrounded by the same albumen, and are so joined each other that their cicatricles, while they are opened in the same moment, constitute only one eye (by me called colliquation), I would have rather believed that a monstrous fetus can be produced with four feet, two heads et cetera; really I don't see anything that can prevent this and I think that such a fetus has been produced from the egg of Fabrizi.

[284] Veruntamen ubi duo vitelli distincti fuerint, duabus tunicis propriis dissepti, et grandinibus suis, albuminibus, caeterisque ad foetus generationem necessariis instructi: cum Aristotele concludendum censeo, tale ovum, ut partes omnes (praeter corticem) duorum ovorum habet, ita et potentias quoque obtinere; ac, nisi infoecundum aut urinum fuerit, duos plerumque foetus producturum, raro autem monstrum singulare.

Nevertheless, to say the truth, when two yolks are divided, separated by two own tunics and endowed with their chalazae, with the albumens and the other things necessary to the generation of the fetus, I think that with Aristotle we have to conclude that such an egg, like it possesses all the parts of two eggs (except the shell), likewise it has to possess its powers, and, except being infertile or windy, for the more it will produce two fetuses, but seldom only a monster.