Two Kinds of Spermatozoa. 



57 



somes of the larger cell divide equally, thus producing two sper- 

 matids with three chromosomes each. These spermatids become 

 spermatozoa. They correspond in their mode of development to 

 the "female-producing" spermatozoa of other insects. Hence 

 we can understand why all of the fertilized eggs become females ! 



The question still remains as to how the males and the sexual 

 females are produced from the parthenogenetic eggs. Here I have 

 some observations to report which seem to indicate how this 

 process takes place. 



I find that the somatic cells of the males of the species referred 

 to above contain only five chromosomes. These five give in the 

 spermatogenesis the reduced number three by two uniting with 

 each other and the third having no partner. I find that the somatic 

 cells of the female contain six chromosomes. It follows that at 

 some time in the life-cycle of the parthenogenetic eggs one chromo- 

 some disappears in those eggs that become males, while the full 

 number is retained in the female. It seems plausible that this 

 change takes place in the formation of the single polar body given 

 off by the parthenogenetic egg. 



The results seem to show that while the sex of the stem-mother 

 is connected with the presence of "female-producing" sperma- 

 tozoa, the production of males and of sexual females is dependent 

 on a process that takes place in the egg analogous to the same 

 process that takes place in the spermatogenesis of other kinds of 

 insects. Hence it follows that the egg as well as the sperm has 

 the power of determining sex by regulating the number of its 

 chromosomes. 



31 (287) 



Physiological problems of the geographical distribution of 

 Partula in Polynesia, with demonstration of specimens. 



By HENRY E. CRAMPTON. 



[From the Department of Zoology, Columbia University^ 



The speaker described briefly the geographical features of the 

 distribution of Partulre in Polynesia, known through the researches 

 of Mayer, Garrett, Cuming, and others, as well as from personal 



