Germ-Cells in Chrysomelid Beetles. 249 



beim Miinnchen, welclier nicht mit zur Bildung der Hodenfollikel ver- 

 brauclit wird, die Aulage zu einer weiblichen Genitaldriise darstellt." 

 Other workers have not sustained Ileymon's interpretation. 



Several papers on the embryology of Blatta (^Phyllodromia) ger- 

 manica were published by Cholodkovsky (1890-91). This author 

 differed in some points from Heymons (1890-91). He found the 

 primitive germ-cells always lying in the dorsal wall of the coelomic 

 cavities pre-eminently if not exclusively in the fifth and sixth abdom- 

 inal segments. The number of germ-cells increased either by division 

 or by the addition of new cells which penetrated into the coelom. 

 As the embryo grew dorsalward around the yolk, the germ-glands 

 were carried to a point on either side of and dorsal to the mid- 

 intestine. Cholodkovsky did not agi-ee with Heymons that the germ- 

 cells differentiated from mesoderm-cells, but held that they probably 

 were derived from yolk-cells. 



Stenobothrus variabilis was studied by Graber (1891). The first 

 distinct rudiments of the gefm-giands were found as two large 

 faintly stained cells differentiated from the visceral layer of the 

 dorsal "Mesoblastdivertikel." At the end of the embryonic period 

 the sexual organs appeared as two strands lying close to one another 

 on the dorsal side of the posterior region of the mid-intestine. 



The germ-glands of Mantis rcligiosa seemed to Graber delayed in 

 their development as compared with those of Stenobothrus, for, in 

 the former, they still retained their lateral position at the end of 

 embryonic life. 



Wheeler's (1893) paper on Xipliidium ensiferum and other 

 Orthoptera contains a short account of the development of the germ- 

 glands. In the above named species the first sign of the primitive 

 germ-cells was not discovered until the somites were established as 

 distinct sacs. The germ-cells at this time lay in the splanchnic 

 walls of the somites of the first to the sixth abdominal segments ; 

 one group was found in the tenth abdominal segment. They were 

 larger and paler than the mesoderm-cells and were thought to have 

 been derived from the latter. A cluster of cells was formed by the 

 mitotic division of these primary germ-cells. The somites that bore 

 germ-cells each sent out a solid diverticulum which connected with 



