AND THE LOWER ANIMALS. 257 



This is what Herold saw,* and what had been also 

 observed by Siebold. Let us suppose that — accident- 

 ally in some species, normally in others — the vital 

 energy of the ovum is unusually intensified; then 

 this ovum will become capable of producing by itself 

 alone a complete animal, and we shall have partheno- 

 genesis in all its stages, such as it is in the silkworm 

 and the other species we have spoken of. 



Seen from this point of view, parthenogenesis, it is 

 true, is not explained, but at all events it is associated 

 with other phenomena, and that alone allows us to go 

 a step further. 



Fundamentally, and from the period of the germinal 

 vesicle condition, f the corpuscle which will eventually 

 become the ovum is formed by the same process as 

 that which gives rise to the bud. 



Both result from the accumulation at a given point 

 of a certain quantity of plastic material, abstracted 

 from a pre-existing individual. Both owe their first 

 origin to a process of growth. 



Now, we have said already that the growth of a 

 living being cannot be indefinite. This is why re- 

 production by buds exhausts itself or is arrested. 

 Reproduction by unfecundated ova should also have 

 a limit. 



Here the great importance of the male sex makes 

 itself apparent. ■ But before the reader can grasp the 



# " Disquisitiones de Ammalmm Vertebris carentium in ovo For- 

 matione." 1838. 



t In my memoirs on the embryogeny of Hermella and Teredo, I 

 stated my reasons for believing that the germinal vesicle precedes 

 all the other elements of the egg. I believe that in the commence- 

 ment it is a homogeneous spherule devoid of an enveloping 

 membrane. 



