FUNCTIONAL SIGNIFICANC E —.MITOCHONDRIA 487 



The adherents of the chromosome hypothesis in this coun- 

 try and elsewhere are naturally opposed to this view. It is 

 said that the cases in which it has been shown that mitochondria 

 pass into the egg on fertilization are exceptional and the crucial 

 cases are those in which no mitochondrial substance passes into 

 the egg. This Lillie believes to be the case in nereis. Mito- 

 chondria generally occur in the middle piece and tail of the sper- 

 matozoon, though this is not always true. Lillie ('12, p. 418) 

 says that "the middle piece and tail of the spermatozoon do not 

 enter in the fertilization of Nereis." He admits (p. 426) that 

 "it is possible that the fixation granules introduced by the sper- 

 matozoon represent a cytoplasmic element." So that, until 

 new facts are discovered, through the use of mitochondrial 

 methods of technique, the case of nereis does not offer an insur- 

 mountable barrier to the acceptance of the view that mitochondria 

 play a part in inheritance. Notice, the claim is not made that 

 mitochondria constitute the sole material basis of heredity, 

 because even though there be a cytoplasmic heredity in some 

 forms it does not follow that it is universal, quite apart from 

 the fact that such a statement would be absurd. It is interest- 

 ing to observe that Wilson ('14, p. 352) has recently admitted 

 the possibility that ^mitochondria may function in heredityr 



To my mind the greatest obstacle in the acceptance of the 

 view propounded by Benda and Meves is our suspicion of the 

 chemical nature of mitochondria. If it is true that they are 

 phospholipins it is hard to regard them as carriers of heredity 

 even though they contain albumin also. It cannot be denied 

 that, chemically, chromatin appears to be best fitted to play 

 the part of heredity carrier. Even, should it be shown that mito- 

 chondrial substance passes over in fertilization in all animals it 

 may indicate nothing more than that a living portion of the 

 sperm, capable of metabolism, enters the egg. It is a mistake, 

 however, to arrive at a hasty conclusion because those who 

 make the conservative statement that mitochondria play some 

 part in heredity occupy just as secure a position as those, on 

 the other hand, who claim that chromatin is the sole heredity 

 carrier. 



