300 N. M. Stevens. 



I have as yet been able to find no satisfactory explanation of the 

 fact that in the four species in which the spermatogenesis has been 

 examined, one of the nine chromosomes behaves so peculiarly, 

 sometimes dividing synchronously with the others, sometimes 

 precociously in both maturation mitoses. One naturally 

 wonders if this chromosome is in any way homologous with the 

 heterochromosomes of insects, whose distribution is closely con- 

 nected with the determination of sex. Of course in a hermaphro- 

 dite organism, there is no question about determination of sex, 

 as the two sexes are combined in one individual, and all fertilized 

 eggs must contain both male and female sex determiners, or at 

 least must be able to produce both male and female germ cells. 



abed ®fgh 



I 



Fig. I. Forms which the bivalent chromosomes assume in prophases and 

 metaphases of the first spermatocyte. 



So far as the chromosomes are concerned, there is no evidence of 

 any such reducing mitosis as might give oogonia, oocytes and ova 

 purely female, and spermatogonia, spermatocytes, and spermato- 

 zoa purely male. If sex determiners are present in the germ cells, 

 both must be present in both oocytes and spermatocytes and re- 

 duction must give both eggs and sperm of two kinds with refer- 

 ence to sex. Selective fertilization would then be necessary to 

 give eggs containing both determiners, and capable of producing 

 hermaphrodite organisms. It may then be possible that the 'be- 

 sondere Korper' discovered by Elpatiewsky is a mechanism for 

 determining dominance of the sex determiners in the male and 

 female germ cells; i.e., determining that one pair of primary germ 

 cells shall give rise to ovaries, the other pair to testes. In sup- 

 port of this suggestion it is important to determine whether any- 

 thing comparable to this 'besondere Korper' is present in the 



