AND THE LOWER ANIMALS. 161 



TMs mode of reproduction was first pointed out by 

 Ehrenberg, the distinguished Berlin micrographer,* 

 who afterwards discovered the zoosperms also of these 

 animals. The Hydra, then, is hermaphrodite, and pro- 

 pagates both by ova and buds. But — and this is a 

 fact of the utmost importance — the buds are always 

 produced first, and the Hydra perishes as soon as it 

 has produced ova. Thus, there springs from the 

 Hydra's egg a simple individual — a scolex — capable 

 of producing many others like itself, and which can 

 also push out buds, but which ends as the parent does, 

 by assuming the sexual attributes. 



It is the same as if a butterfly's egg gave rise to 

 an animal having all the external characters of the 

 perfect insect, but devoid of reproductive organs, 

 having the power of producing by gemmation other 

 beings resembling itself, which, like it, would be 

 capable of acquiring at a later period the male and 

 female generative bodies. 



Here we observe geneagenesis in its simplest form, 

 deprived of all accessory circumstances, and of all the 

 complications which result from change of form. The 

 several generations of scolex are exactly similar, and 

 each scolex is directly transformed into a proglottis, the 

 strobila stage being entirely absent. The very sim- 

 plicity of the process shows what is really its most 

 fundamental part — viz., the production of several 

 generations from a single germ. 



The compound ascidians show us something ad- 

 ditional. 



In these the ovum develops a scolex, which becomes 

 fixed, acquires well-marked reproductive organs, and 



• " Die fossil en Infusorien/' 1837. 



M 



