DAVIS: SPERMATOGENESIS. 137 



the rest stage between the two maturation mitoses." In the present 

 state of our knowledge it seems impossible to homologize this element 

 with the monosome. In the case of Periplaneta Moore and Robinson 

 (-.05) have denied the presence of the monosome. The deeply staining 

 body which can be seen applied to the nuclear membrane during the 

 growth period they believe to be a plasmosome, which is extruded 

 from the nucleus during the prophase of the first division. This 

 seems in the highest degree improbable, since Stevens (:05") has 

 found a typical monosome in the closely related germs Blatella. It 

 seems probable that Moore and Robinson have confused the mono- 

 some and plasmosome. I have noticed that in many of the Acrididae 

 during the late growth period, when the monosome stains less deeply 

 and is usually greatly elongated, the plasmosome tends to take the 

 chromatin stain and appears very similar to the monosome at an 

 earlier stage. Baumgartner (:04) has noticed in Gryllus a similar 

 tendency for the plasmosome to take the chromatin stain. 



Recently Foot and Strobell ( :07) have denied the presence of a mono- 

 some in Anasa, where it had been described by Wilson and by Mont- 

 gomery. Foot and Strobell maintain that in the spermatogonia of 

 Anasa there are twenty-two chromosomes, not twenty- one as held by 

 Wilson and by Montgomery, and that the deeply staining element 

 which is present in the spermatocytes during the growth period is 

 simply a plasmosome, which is extruded from the nucleus in the pro- 

 phase of the first division. They have failed to find any chromosome 

 which does not divide in both divisions. However, Wilson (:07) 

 asserts that reexamination of his preparations has confirmed the accu- 

 racy of his previous results. 



I think there can be no doubt that a monosome occurs in most of 

 the Orthoptera. The cumulative evidence of a large number of 

 investigators cannot be lightly put aside. I fail to see how in many 

 cases a more conclusive demonstration could be desired. This is 

 especially true of Steiroxys, where I have been able to follow the 

 monosome continuously from the primary spermatogonia to a late 

 stage in the metamorphosis of the spermatid. 



In the spermatogonia of the Orthoptera the monosome is always 

 one of the larger chromosomes and sometimes may be much larger 

 than any of the autosomes. This is the case in Xiphidium (McClung, 

 '99), Orphania (de Sin^ty, :01) and Gryllus (de Sinety, :01; Baum- 

 gartner, :04; Gutherz, :07). In the spermatocytes the monosome 

 IS always a conspicuous element, where, at least in the early growth 

 stages, it forms a more or less compact body applied to the nuclear 

 membrane and often in close connection with a plasmosome. 



