Internal Factors of Sex Determination 401 



the evidence to see whether, in these cases, sex is determined by 

 the kind of division that takes place in the sperm. 



The Formation of Male and Female Producing Spermatozoa 



It has been known since 1836 that two kinds of spermatozoa 1 

 are present in the snail Paludina, and both kinds have been found 

 in the upper part of the oviduct where the egg is fertilized, but 

 whether both kinds are functional is not known. Meves has 

 studied recently the method of formation of these two kinds of 

 spermatozoa. The hair-like spermatozoa resemble the ordinary 

 forms of spermatozoa, the worm-like spermatozoa have a long, 

 rounded, worm-like shape, as the name implies. In the forma- 

 tion of the worm-like form, a peculiar and perhaps a degener- 

 ate process occurs. Instead of containing the reduced number 

 (seven) of chromosomes, it gets only a single chromosome. 



Two kinds of spermatozoa are also described by Meves in the 

 butterfly Pygaera. One of the two kinds contains no chromatin 

 material whatever. It is headless and perhaps functionless also. 



In addition to these cases giant spermatozoa, double the size 

 of the normal ones, have been described in several groups, espe- 

 cially in amphibians and birds. They are due to the incom- 

 pleteness of one or of both of the spermatocyte divisions, and 

 may be only abnormal forms incapable of fertilizing the egg. 



The most remarkable spermatozoa, however, are those in 

 which half of the spermatozoa contain one more chromosome 

 than the other half. 



Henking discovered in 1890 the presence of a peculiar chro- 

 matin-like body in the spermatogenesis of the bug Pyrrhocoris. 

 It has since been shown that this body is a true chromosome, 

 although it behaves differently from the other chromosomes in 

 certain respects. The more recent work of McClung, Mont- 

 gomery, Paulmeier, Sutton, Stevens, and especially of Wilson, 

 has cleared up some of the most important questions connected 

 with the behavior of the accessory chromosome. 



1 Discovered by von Siebold. 



