Chromatin as ''TIcredifary Stthsfnnre"' r]47 



making out that there are two sorts of spermatozoa from 

 one and the same male in certain insects, the diirerence be- 

 tween the two being that the head of one kind {'onhiins an 

 element or body not present in the other. At first tliere was 

 difference of view as to the anatomical nature of tliis extra 

 element. Some regarded it as akin to the nuckokis rather 

 than to the chromosomes. The idea of dimorphic spenna- 

 tozoa was first clearly expressed by H. Henking as follows, 

 "I believe every unbiased observer will view with me this 

 S2)herical element [of the sperm head J sharply distinguish- 

 able from the other chromatin, as the niK-lcar body [present 

 in part of the spermatids]. Thus is revealed the important 

 fact that we have two kinds of spermatozoa : one kind pos- 

 sesses a nucleolus, the other does not^ ^■' 



C. E. McClung, another student of spermatogenesis, first 

 suspected that these two kinds of spermatozoa have some- 

 thing to do w^ith the two sexes. The important paper in 

 which this hypothesis is set forth was published in 190^2, 

 and within the brief period since that date, the hypothesis 

 has been supported and extended by such a mass of obser- 

 vation that its universality for at least the animal kingdom 

 seems not improbable. 



The exact terms in which jNIcClung stated the hypotheses 

 merit attention. He says, "Briefly stated, then, my con- 

 ception of the function exercised by the accessory chroiuo- 

 some is that it is the bearer of those qualities which pertain 

 to the male organism, primarj- among which is the faculty 

 of producing sex-cells that have the form of spermatozoa." "' 

 Noteworthy for our discussion is the difference of viiw 

 concerning the chemico-morphological nature of the extra 

 element in the spermatozoan as shown by these two ({nota- 

 tions. It was regarded as sharply distinguished troiii the 

 chromosomes by Henking, but as a true chromosome by Mc- 

 Cluno-. The great ]:)re])onderance of later opinion has side<l 

 with McClung, but very recently the (puslion has Ixcn 



