io6 



CYTOLOGY 



CHAP. 



The last case is perhaps the most remarkable, the X group consisting 

 of two large and three very small constituents (Figs. 49, 50). 



The chromosome equipment of the various examples is as follows 

 (omitting Protenor and Lygaeiis, which have already been dealt with) : 

 n' stands for the haploid number of ordinary chromosomes; and the 



AnaphaseR 

 in <S. 



Two classes of 

 spermatozoa,. 



oOo 



O ^* O ^ 



Reduced, number 

 (f chromosomes 

 in the eg^. 



oOo 

 o .-.o _ 



0, •• O 



qOc^is '^oo0 9'5 



o^^o 



o #g 





Mole and/emjale 

 chromx)somje 

 groups. 



Oo.V#og 



OoW'h * 



Fig. 50. 



Diagram of the results of fertilization in Acholla multispinosa. (Payne, B.B., 1910.) 



The sex chromosomes shown in black. 



number of components of the X chromosome is represented by the 

 sufhxed numeral. 



Male. 

 Diploid Group. 



Syromastes (Wilson, 1909a), n'=io 2w' + X2 



Ascaris lumhricoides (Edwards,^ 

 1910), n' = 19 j 



Fitchia (Payne, 1909), n'=iz 

 Prionidus (Payne, 1909), n'=ii 

 Gelastocoris (Payne, 1909), n'—i$ 

 Acholla (Payne, 1909), w'=io 



2W'+X, 



2w' + X,Y 



Gametes. 



Jn' + X, 

 U' 

 p' + X, 



/w' + X. 



U' + Y" 



Female. 

 Diploid Group. Gametes. 



2n' + X,Y |^,^Y 



2n' + X^Y 



2n' + X.Y 



fn' + X, 

 U' + Y 

 (w' + Xg 

 \n' + Y 



2m' + X,X, 



2n' + X,X, 



2n' + X^X.^ 

 2.n' + X3X3 

 2n' + X^X^ 



in' + X,X, 



n' + X2 

 w' + X, 



W' + X2 



W' + Xg 



w' + X, 

 n' + X, 



Thus in Acholla the female group has four more chromosomes than 

 the male, the actual numbers being 30 and 26. 



(4) Behaviour of the Sex Chromosomes during Syndesis and the Meiotic 



Prophase, and outside the Meiotic Phase 



As was illustrated in the case of Lygaeus, the sex chromosomes in 

 the male retain a compact form, while the other chromosomes are in 



