36 THE AMPHIOXUS. 



From the perforation of the mouth and of the first 

 gill-slit the larva begins to nourish itself indepen- 

 dently, -since the } T olk material contained in the egg 

 is quite used up, and the cells of the larva consist of 

 absolutely transparent protoplasm. 



From now onwards the development proceeds very 

 slowly, especially at first, the larva having to make 

 good the material for development, which is quite ex- 

 hausted. 



Thus, while a great part of the most important pro- 

 cesses of development takes up only the short space 

 of forty-eight hours, the further development on the 

 other hand, from the time when the larva must begin 

 to nourish itself, occupies months. 



C. THE LIBERATED EGG, THE EXPULSION OF THE 

 POLAR BODY, AND THE FERTILIZATION. 



The following is Kowalevsky's account of the eggs 

 just liberated. " The ejected eggs lay at first from 

 ten to twenty together in little lumps. Further and 

 repeated observations always resulted in showing 

 that the ejection of the eggs was preceded on the part 

 of the male by an ejection of semen. 



' The eggs just ejected consisted of a dark yolk 



