THE MORPHOLOGY OF FERTILIZATION 75 



logical process that requires experimental methods for 

 its solution. 



h) The mitochondria in fertilization: The other 

 cytoplasmic element that has been claimed to play 

 an important role in fertihzation is the mitochondria 

 (called plastochondria by Meves), which form such an 

 apparently important constituent of all classes of cells. 

 The special protagonist of the significance of this sub- 

 stance in fertilization is Meves, who maintains that 

 it is concerned in the transmission of hereditary char- 

 acteristics, basing this view on the part that he believes 

 it to play in protoplasmic differentiation. He found 

 an apparently very demonstrative case in A scan's 

 megalocephala (Meves, 191 1), the spermatozoa of which 

 contain large numbers of mitochondrial granules in 

 the large cytoplasmic body surrounding the nucleus 

 (cf. Fig. 6). The entire spermatozoon penetrates in 

 this case, and the mitochondrial granules continue to 

 surround the nucleus long after penetration ; by degrees 

 they become intermingled with the mitochondria of the 

 egg, and Meves even hazarded the conjecture that they 

 possibly united by pairing with the mitochondrial gran- 

 ules of the egg; he therefore considered his view that the 

 mitochondria play an important role in heredity justified. 



Pursuing the matter farther Meves (1914) made an 

 exceedingly careful study of the fate of the middle 

 piece of the spermatozoon in the fertilized eggs of 

 echinids. By a veritable triumph of technique he found 

 that this minute fragment could be traced intact into 

 one of the first two cells; in successive cell divisions it 

 always passes intact into one of the daughter-cells 

 only, and may be found in the eight-celled stage either 



