Scientific Proceedings. 09 0 21 



somes, and during the maturation process they are so distributed 

 that the small one passes into one half of the spermatozoa, the 

 large one into the other half. 



These facts appear to admit of but one interpretation. Since 

 all of the chromosomes in the female (oogonia) may be symmetric- 

 ally paired, there can be no doubt that synapsis in this sex gives 

 rise to the reduced number of symmetric bivalents, and that con- 

 sequently all the eggs receive the same number of chromosomes. 

 This number (n in Anasa, J in Protenor or Alydus), is the same 

 as that present in those spermatozoa that contain the ' ' accessory" 

 chromosome. It is evident that both forms of spermatozoa are 

 functional, and that in type A, females are produced from eggs 

 fertilized by spermatozoa that contain the " accessory" chromo- 

 some, while males are produced from eggs fertilized by spermatozoa 

 that lack this chromosome (the reverse of the conjecture made by 

 McClung). Thus if n be the somatic number in the female, 71/2 is 

 the number in all of the matured eggs, 71/2 the number in half of 

 the spermatozoa (namely, those that contain the " accessory") and 

 71/2— 1, the number in the other half. Accordingly : 



In fertilization 



n n 

 Egg - + spermatozoon - = n (female). 



„ n „ n 



Egg - -f spermatozoon - — 1 =ji — 1 (male). 



The validity of this interpretation is completely established by 

 the case of Prote7ior y where, as was first shown by Montgomery, 

 the "accessory" is at every period unmistakably recognizable by 

 its great size. The spermatogonial divisions invariably show but 

 one such large chromosome, while an equal pair of exactly similar 

 chromosomes appear in the oogonial divisions. One of these in 

 the female must have been derived in fertilization from the egg- 

 nucleus, the other (obviously the "accessory") from the sperm- 

 nucleus. It is evident, therefore, that all the matured eggs must 

 before fertilization contain a chromosome that is the maternal mate 

 of the "accessory" of the male, and that females are produced 

 from eggs fertilized by spermatozoa that contain a similar group 

 (i. e., those containing the "accessory"). The presence of but 



