104 



CYTOLOGY 



CHAP. 



The two different ways of obtaining the same end result — the pro- 

 duction of the two types of spermatozoa in equal numbers — may be 

 represented in a diagram as follows : 



Spermatocyte I. 



Spermatocyte II. 



Spermatid. 



First division equational. 

 Second division reductional. 



First division reductional. 

 Second division equational. 



(3) Various forms of the X and Y Chromosomes 

 A frequent feature of the X chromosome is that it is compound, 





^ife^- 



B 



• • • % « 



♦ ♦.♦ 



«.Jl 



•;.:t4i\^'?;-"' 





X •- -Y 





X 



H 



Fig. 48. 



The chromosomes of Gelastocoris. (Payne, B.B., 1909.) A, 9 diploid group, 30 + 2X4=^38 chromosomes; 

 B, i diploid group, 30 + .X4 + Y = 35 chromosomes; C, metaphase l.,S, 15 + X4 + Y = 20 chromosomes ; D. 

 metaphase II., i ; the sex chromosomes are in the middle of the ring, the four components of the X chromo- 

 some in a group opposed to the single Y chromosome which is partly underneath them; E, metaphase II., <5; 

 F, anaphase II., (J ; G, H, polar views of anaphase II., J — G with the Y chromosome, H with the X group. 



