I 54 FERNANDUS PAYNE. 



divided in one division but not in the other. According to these 

 interpretations, then, the accessory chromosome would be bivalent. 



McClung, however ('01), maintained the accessory to be uni- 

 valent. Wilson ('05 and '06) has shown in the Hemiptera 

 heteroptera that Paulmier ('99) and Montgomery ('01) were 

 wrong in their interpretation of the origin of the accessory chro- 

 mosome, that the small bivalent divides in both divisions, and 

 that the accessory chromosome is a univalent spermatogonial 

 chromosome which divides in only one division, and this was 

 confirmed by Montgomery ('06) in opposition to his earlier con- 

 clusion. 



The results of Gross ('04 and '06) have been more or less of 

 a hindrance to the correct interpretation of the accessory chromo- 

 some. Wilson ('09) again has shown that Gross was mistaken 

 in the case of Pyrrhocoris and that the accessory chromosome is 

 here univalent. He confirms, however, Gross's results on the 

 male cells of Syromastes. The spermatogonial number is even 

 (22), and the accessory chromosome is here, in fact, bivalent, 

 but it divides in only one division. Gross figured the same 

 number of chromosomes in both male and female cells, but 

 Wilson inferred (not having material) that the oogonial cells 

 would show 24 chromosomes, since the accessory chromosome 

 is bivalent. In an addendum to his last paper ('09^) Wilson 

 states that his inference has proven true and that the female 

 cells of Syromastes have, in fact, 24 chromosomes. In principle, 

 therefore, Syromastes conforms to those forms in which the 

 accessory chromosome is univalent. 



Another contradiction occurs in the work of Foot and Strobell 

 ('07) on Anasa tristis, who assert that the densely staining body 

 in the rest stages of the spermatocytes is a true nucleolus and 

 not a chromosome nucleolus formed by the accessory chromo- 

 some as described by Wilson ('05 and '06) and Montgomery 

 ('06). Wilson's reexamination of his preparations with addi- 

 tional studies on smear preparations and living material, led to 

 the same conclusion as before. Lefevre and McGill ('08) have 

 reexamined the form and their results agree in every detail with 

 those of Wilson and the later ones of Montgomery. From the 



