18 Edmund B. Wilson 



g. Lygaeus turcicus 



In this species the inequality of the idiochromosomes is nearly 

 or quite as great as in Euschistus variolarius, but the differentia- 

 tion of the chromosome-pairs is less marked than in that species, 

 and the small pair cannot be distinguished with certainty in any 

 of the stages. In the spermatogonial groups, accordingly, only 

 the small idiochromosome is markedly smaller than the others 

 (Fig. 5, c, </); and hence its lack of an equal mate is rendered very 

 conspicuous. In the female the small idiochromosome is absent 

 as usual and all the chromosomes are equally paired (Fig. 5, /, ^). 

 The idiochromosomes cannot be distinguished from the ordinary 

 chromosomes. 



b. Podisus spinosus 



In this species both sexes show sixteen chromosomes. In the 

 spermatogonial groups (of which I am now able to give a better 

 figure than the one in my first paper) the small idiochromosome 

 appears relatively larger than in any of the foregoing species, 

 though still not more than half the size of any of the others 

 (Fig. 5, y). In the female (follicle-cells, Fig. 5, k) all the chro- 

 mosomes are equally paired and the small idiochromosome is 

 absent, but owing to the relatively large size of the latter in the 

 male the chromosome-groups of the two sexes do not show so 

 obvious a contrast as in the foregoing cases. 



Resume and Conclusions Regarding the Second Type 



In all the forms described under this type the two sexes show 

 the same number of chromosomes but differ in that the male 

 groups include a large and a small idiochromosome while the 

 female groups have two large idiochromosomes of equal size. 

 This result agrees with that already reached by Stevens ('05) in 

 the case of the beetle Tenebrio, and involves the same conclusions 

 that she has indicated. Since all the chromosomes of the oogonial 

 groups are equally paired, it is evident that all the matured eggs 

 must contain half such a group, one of the chromosomes being 

 the maternal representative, or mate, of the large idiochromosome 



