A STUDY OF SOMATIC CHROMOSOMES. 353 



be expected to be arrived at from the somatic mitoses with their 

 long chromosomes." 



In the Diptera Metz has reported that the somatic chromo- 

 somes are closely paired together. In the case of Sarcophaga 

 and Fucellia the groups of 24 and 48 chromosomes represent 

 multiple groups, and the arrangement of the chromosomes is in 

 tetrads rather than in pairs. 



In her paper on Culex pipiens Miss Taylor takes up in detail 

 the work of Miss Stevens on Culex pun gens, and is evidently 

 unaware of the fact that Miss Stevens published a paper on 

 pipiens a few years later. Miss Taylor considers the presence 

 of six chromosomes in Miss Stevens's material as due to a pre- 

 cocious splitting or division of the diploid number of three. Miss 

 Stevens described a parasynapsis or side-by-side union of the 

 chromosomes in each cell generation. This Miss Taylor thinks 

 may offer a clue to the conditions she found in pipiens, namely 

 that in this species "parasyndesis" is converted "into actual 

 fusion, thus resulting in the formation of three out of six chromo- 

 somes." She offers as an alternative the suggestion that one 

 of the pronuclei does not take part in development. Her results 

 are not entirely convincing, especially since she found stages in 

 many of the somatic cells comparable to synizesis stages in 

 spermatogenesis. This seems to show that perhaps her material 

 was not of the best. Metz has found that the method of securing 

 the preparations of the testes employed by Miss Taylor, namely 

 that of fixing either the whole or a large part of the insect entire, 

 results in a "clumping or running together of the chromosomes, 

 which is exactly the kind of behavior that would cause pairs to 

 give the appearance of single chromosomes" (p. 226). He agrees 

 with Miss Stevens's observations. 



In the spermatogenesis of the bee, according to Meves, there 

 is no reduction division. Nachtsheim considers 32 as the normal 

 number. The 16 chromosomes in the oogonia are bivalent, 

 likewise the 8 which form the haploid number. Similarly a 

 haploid number of 8 chromosomes has been reported in the 

 spermatoctyes, which is due to this " Chromosomenkoppelung." 

 Here these also would be bivalent. Though the reports of 

 several investigators tend to show that the number of chromo- 



