CHROMOSOME STUDIES 227 



genus (de Sinety, Gerard, Davis, Meek). With the exception 

 of Davis ('08, figs. 17, 21), none of these authors have seen 

 the archoplasmic bridge or constriction at the apex of the Vs. 

 Though Davis's figures (17-21) show it, it is not mentioned 

 in the text. The V's in every case have arms more or less un- 

 equal in length. 



McClung ('05, figs. 1, 7, 8, 9; '15, fig. 84) has described a 

 single V-shaped chromosome in three species of Hesperotettix 

 ( cf ) which is made up by hnkage proximally of an autosome 

 with the sex chromosome. The sex-chromosome portion may 

 be recognized by the smoothness of its surface. In Mermiria 

 also he has described a V-chromosome ; this differs from that of 

 Hesperotettix in that the sex chromosome here seems to be 

 attached to the distal end of one of the two autosomes entering 

 into the V. McClung believes that in this multiple chromo- 

 some of the first spermatocyte division two tetrads, as well as 

 the sex chromosome, are concerned, and that in this division whole 

 tetrads separate from each other. It seems to me that, instead 

 of interpreting the multiple body in this way, we may say that 

 Mermiria has a pair of autosomal V's, to the end of one of which 

 is appended the sex chromosome. The presence of the sex 

 chromosome in the V's of both genera is evidence of the compound 

 nature of these V's, since one limb of the V may be identified 

 by its smooth surface as an individual, specific chromosome 

 (viz., the sex chromosome), while the other limb is shown by 

 its roughness to be similar to the autosomes. Also the number 

 of other autosomes present shows that it must be one of them. 



The V's of Chortophaga, which McClung (fig. 94) interprets 

 as the result of the precocious synapsis of homologous chromo- 

 somes in the spermatogonia, I am inclined to think are not 

 such; they are, instead, V's consisting of non-homologous chromo- 

 somes, similar to those of Chorthippus, in which, however, the . 

 fusion is more Uke that of Notonecta (Browne, '13) or Jamaicana 

 (Woolsey, '15) than of Chorthippus. The non-homologous 

 nature of the limb? of the V's in all these cases may be inferred 

 from the fact that they are always of unequal length. 



JOURNAL OF MORPHOLOGY, VOL. 27, NO. 2 



