GENERATION OF ANIMALS, III. v. 



copulating, for with them copulation goes on for quite 

 a long time, and it is plain here that one is male and 

 the other has a uterus. Also, it would be odd if this 

 characteristic *" were present in a portion of the group 

 and not in the whole of it, just as male and female are 

 found in all the ^'i\ipara. The reason for the ignor- 

 ance of those who make the statement mentioned is 

 that the differences in the copulation and generation 

 of the various animals are manifold, but they are not 

 obWous, and our friends base their study on a few 

 instances and think the same holds good for all. 



So too those who assert that female fishes conceive (2) The 

 as a result of swallowing the male's semen have Jfrnii^" 

 failed to notice certain points. Thus in fact milt is 

 present in the male and eggs in the female at about 

 the same time, and the closer the female is to laying 

 the eggs the more abundant and the more fluid 

 becomes the milt in the male. And just as the 

 growth of the milt in the male and that of the egg 

 in the female is simultaneous, so also the emission of 

 them both is simultaneous : the females do not lay 

 all their eggs at once, but a few at a time, and the 

 males do not emit all their milt at once. All this is 

 as we should expect. In the bird tribe, eggs are in 

 some instances present without impregnation, though 

 such eggs are not numerous and they occur but 

 seldom, most eggs being the result of impregnation. 

 Exactly the same occurs in fish, though to a smaller 

 extent. These spontaneous eggs, both in birds and 

 fish, are infertile unless (in those species where there 

 are males as well) the male sprinkles them. With 

 birds, o\^ing to the fact that the eggs have reached 



" Ihjnamis, i.e., the existence of the two sexes. Cf. the 

 beginning of ch. 5. 



31J 



