212 VITALISM AND SCHOLASTICISM 



Spermato- development.' When the spermatozoon enters 



zoon and t j ie ovum ft causes some alteration in the sur- 

 ovum 



face membrane of the latter which, amongst 



other things, prevents the entrance of further 

 spermatozoa. Loeb thinks that in causing this 

 alteration it sets up the segmentation of the 

 ovum. That there is a close connection be- 

 tween the two events seems undoubted; that 

 they are in relation of cause and effect seems 

 likely. It is quite evident that an artificial 

 stimulus can in certain cases set up segmenta- 

 tion, but never can it cause the fertilisation of 

 the ovum. It may very likely produce the 

 same change in the membrane that is caused 

 by the entrance of the spermatozoon under 

 normal circumstances membrane formation 

 may be necessarily coincident with the libera- 

 tion in the egg of some zymose which arises 

 form a pre-existent zymogen. But we are still 

 some way off any assurance that the main 

 object of the spermatozoon in inducing the 

 development of the egg is this surface altera- 

 tion. It may be the initial effect; very prob- 

 ably it is ; but since the main function of the 

 spermatozoon must be the introduction of 

 germplasm from the male parent, it is too much 

 for anyone to ask us to believe that its main 

 function is concerned with surface alteration." 

 Here we may break off from the quotation 



