Sperniatogeuesis 475 



the work of McClung, de Sinety, Sutton, Baumgartner and Stevens 

 covers numerous species in several families, we have a right to 

 question the views of these other three observers. All three hold 

 that the heterochromosome which they describe is formed from 

 two spermatogonial chromosomes and divides in both spermato- 

 cyte divisions. 



Moore and Robinson ('05) claim that the odd chromosome in 

 Periplaneta americana is only a plasmosome which dissolves 

 before each division and is reconstructed after it. 



Odonata 



The paper of McGill ('04) on Anax Junius seems to show the 

 same confusion which Wilson has discovered in Paulmier's work 

 on Anasa tristis. McGill finds an even number of chromosomes 

 in the spermatogonia, two of them small. These she identifies 

 with the chromatin nucleolus of the rest stage and the odd chromo- 

 some, which divides in the first division and not in the second. If it 

 could be shown that there are only 27 chromosomes in the sper- 

 matogonial plate, and that the odd chromosome is one of the larger 

 ones, this form would fall into line with other work. 



Lepidoptera 



The early investigators in this field, Platner ('86) and Verson 

 ('94) paid no attention to the chromosomes. I have not been 

 able to read Toyama's papers, but the references to them by 

 McClung indicate that the work is not very satisfactory. Stevens 

 ('06b) gives a few figures for two species. There are two con- 

 densed bodies throughout the growth period, which fuse in pro- 

 phase like the m-chromosomes in Alydus (Wilson, '05c), and this 

 body divides in both divisions like the equal "idiochromosomes" 

 of Nezara. 



Coleoptera 



The only work on the Coleoptera which deals with the hetero- 

 chromosomes is that of Stevens ('05b and '06b) and of Nowlin 

 ('06). Some of the beetles have an odd chromosome and others 

 have an unequal pair in which the large member of the pair is the 



