396 Edmund B. Wilson. 



by Montgomery ('01) in Protenor, has been more recently shown 

 by Gross ('04) to exist in Syromastes; and I have also been able to 

 demonstrate the same fact in Alydus and in Anasa (Paulmier 

 having been in error in his identification of the accessory with the 

 small chromosome in the last-named form). 



The second type includes the idiochromosomes, which in the 

 forms I have studied differ from the Anasa type in four respects 

 (Nezara being an exception in regard to the first of these), namely, 

 (l) in their unequal size, with which is correlated the fact that only 

 a single microchromosome appears in the spermatogonia; (2) in 

 the fact that the final conjugation or synapsis of these bodies is 

 deferred until the prophases of the second division, a result of 

 which is that the first division shows one more than half the sper- 

 matogonial number of chromosomes while the second division 

 shows exactly half the spermatogonial number; (3) in the fact that 

 in case of the idiochromosomes it is manifestly the second division 

 that is the reducing one, while my observations on Lygaeus render 

 it practically certain that the first is an equation-division; (4) in 

 the fact that no accessory chromosome in the usual sense is present 

 and all the spermatozoa receive the same number of chromosomes. 

 In view of these differences it seems expedient for the present to 

 place these two types in different categories. 



It is evident from Montgomery's figures and descriptions that 

 he observed many of the details of the phenomena described in the 

 present paper; but it is equally clear from the varying interpreta- 

 tions that he adopted that he failed to reach any consistent general 

 result regarding the behavior of the idiochromosomes, or to recog- 

 nize the dimorphism of the spermatozoa. For example, it is 

 evident, I think, from his descriptions of Euschistus variolarius, 

 E. tristigmus, Coenus delius, Oncopeltus fasciatus, and Lygus 

 pratensis, that the essential facts in these forms agree with those 

 I have described, the idiochromosomes being in the last named 

 two species of equal size, as in Nezara; but Montgomery offers 

 for each of these cases a different interpretation. In the first 

 named species the idiochromosomes are clearly figured in his first 

 paper ('98, Figs. 171, 188, 189, etc.), and in Fig. 214 they are 

 shown separating in quite typical fashion in the second division 

 (the smaller one designated as a "chromatin-nucleolus"); but it 

 is evident from the descriptions given in both this and the following 

 paper ('01, i) that he did not reach a correct interpretation of the 



