ON GENERATION. 223 



me, nevertheless, this does not appear likely ; because it is cer- 

 tain that the whole ovary being removed, the uterus secundus 

 also diminishes in size in the same proportion, and shrinks into 

 a mere membrane, which contains neither any fluid nor any 

 albumen. Fabricius proceeds : "The ova centenina are met with 

 of two kinds : one of them being without a yelk, and this is the 

 true centenine egg, because it is the last which the hen will 

 lay at that particular season she will now cease from laying 

 for a time. The other is also a small egg, but it has a yelk, 

 and will not prove the last which the hen will then lay, but is 

 intermediate between those of the usual size that have preceded, 

 and others that will follow. It is of small size because there 

 has been a failure of the vegetative function, as happens to the 

 peach, and other fruit, of which we see many of adequate size, 

 but a few that are very diminutive." This may be in conse- 

 quence of the inclemency of the weather, or the want of sun, or 

 from defective nutriment in point either of quantity or quality. 

 I should not readily allow, however, that the eggs last laid are 

 always small. 



Monstrous eggs are not wanting; "for the augurs," says 

 Aristotle, 1 " held it portentous when eggs were laid that were 

 all yellow; or when, on a fowl being laid open, eggs were found 

 under the septum transversum, where the rudimentary eggs of 

 the female usually appear, of the magnitude of perfect eggs. 



To this head may be referred those eggs that produce twins, 

 that have two yelks. Such an egg I lately found in the uterus 

 of a fowl, perfect in all respects, and covered with a shell ; the 

 yelks, cicatriculse, and thicker albuminous portions being all 

 double, and the chalazae present in two pairs : a single thinner 

 albumen, however, surrounded all these, and this in its turn 

 was included within the usual double common membrane, and 

 single shell. For, indeed, although Aristotle says that fowls 

 always lay some eggs of this kind, I shall hardly be induced 

 to believe that this does not occur against the ordinary course 

 of nature. And although twin chicks are produced from 

 such eggs as I have ascertained in opposition to the opinion 

 of Fabricius, who says that they produce chicks having four 

 legs, or four wings and two heads, which, however, are not 



1 Aldrovand. Ornithol. lib. xiv, p. 260. 



