CHAP, iv.] OF ANIMAL GENERATION. 333 



the other histological elements by their motility, and especially 

 by their fecundating property, veiy inferior on the other hand by 

 their structure. 



All the particles of pollen, all the spermatozoids and sperma- 

 tozoaries are endowed with the fecundating property. But it seems 

 established by experiments of artificial fecundation, that a single 

 particle of pollen, a single spermatozoary cannot alone fecundate 

 an ovulum. The ovum needs veritably and literally to be impreg- 

 nated with fecundating molecules. There is a certain minimum 

 which does not suffice to give the necessary impulsion. 



We have seen what great analogy exists between the male 

 ovulum and the female ovulum. In the inferior animals and 

 even in the superior animals, at a certain period of embryonary 

 evolution, the analogy extends to the whole male and female 

 generative apparatus. At a particular moment of the intra- 

 uterine life it is impossible to distinguish the male embryon from 

 the female embryon, and in many invertebrates the difficulty 

 persists during the whole duration of life, to such a point indeed 

 that men like Cuvier, Carus, and Blainville never succeeded in 

 distinguishing from each other the ovarium and the testicle of 

 the gasteropods. 1 



The ovulum and the sperm atozoaries have another property in 

 common, the property of reviviscence. Spermatozoaries desiccated 

 can get back their motility after a very long time, when they are 

 humected anew ; and M. Davaine was able to keep for five 

 years, without killing them, in a solution of chromic acid, at 

 2 in 100, the eggs of the lumbricoid ascarides of the Greek 

 tortoise. As for the vegetal seeds, we know that some of 

 them can still germinate after thousands of years. 

 1 Duges, loc. cit. t t. I., p. 231. 



