102 SEX INHERITANCE 



the sexual females. The other stem mother XxXx', 

 produces eggs, which, after extruding one polar 

 body, give rise to the migrants bearing small eggs. 

 Prior to the time when these small eggs are about to 

 give off their single polar body, the two large X's 

 conjugate and the two small x's conjugate, and when 

 the polar body is given off one large and one small X 

 pass out, and one large and one small X remain in the 

 egg. In other words there is at this time a reduction 

 in the number of sex chromosomes, and, as a conse- 

 quence, a male is produced. Now as the diagram 

 shows, Xx may remain in the egg and Xx' pass out ; 

 or, in other eggs, Xx' may remain in the egg and Xx 

 may pass out. There will be, in consequence, two 

 kinds of males, one Xx, the other Xx', and as 

 stated, two kinds of female producing sperm Xx 

 and Xx'. 



Thus the life cycle is brought back to the starting 

 point. It may be added that so far as the chromo- 

 somes other than the X chromosomes are concerned 

 there is no synapsis and no reduction to the haploid 

 number in either line until the maturation divisions 

 of the third or sexual generation occur. The life 

 cycle of this species illustrates three points: 



First. That all of the sperm are female producing, 

 because the male-producing class of sperm degener- 

 ates, as has been shown by direct observation. 



Second. That the parthenogenetic females can 

 produce males through the elimination of two 

 chromosomes. The female contains four sex chro- 

 mosomes and the male two. The elimination of the 



