ORTHOPTEROIDEA {PANORTHOPTERA) 245 



maximum size during blastokinesis, after which they gradually become 

 smaller. The subesophageal body is still in evidence in the freshly 

 hatched grasshopper, where it occupies a small space beneath the ante- 

 rior end of the crop. Roonwal agrees with Heymons in regarding this 

 body as excretory in function. 



The germ cells are first distinguishable in the 112-hour stage (Fig. 

 160) as cells that are larger and whose nuclei are poorer in chromatin than 

 those of the adjacent mesoderm. They lie in the median walls of the 

 dorsal pouch of the coelom of the second to the fifth abdominal segments. 

 They are at first segmental but afterward extend into the intersegmental 

 regions as well. Soon they can be traced as far back as the tenth abdom- 

 inal segment. Each gonad rudiment is spindle-shaped and composed 

 of five parts: a terminal filament, a dorsal cell mass, a central cell mass 

 consisting of the germ cells and mesoderm cells, a small ventral cell mass 

 lying below the central mass, and the follicular cells which limit the gonad 

 rudiment from the outside. In the male the dorsal cell mass becomes 

 incorporated into the central cell mass which forms the testes proper. 

 The ventral cell mass gives rise to the gonadal part of the vas deferens 

 which shows no lumen at the time of hatching. In the female the dorsal 

 cell mass forms the germarium, and the central cell mass contains the 

 oogonia and the interfollicular cells. The ventral cell mass forms the 

 egg calyx, and the follicular cells give rise to the outer membrane of 

 the ovarioles and of the egg calyces. The gonadal portion of the genital 

 ducts, as noted above, are formed of the ventral cell mass. In many of 

 the abdominal segments the ventral coelomic pouches form ampullae 

 which usually remain connected for some time with the rest of the 

 coelomic walls by means of solid strands. In the female the ampullae 

 are formed in the third and fourth and the sixth to the tenth abdominal 

 segments. All these, except the pair belonging to the ninth segment, 

 have a distinct lumen until sometime after blastokinesis. Strands that 

 connect the ampullae disappear sooner or later. Portions of the strands 

 in the seventh and eighth segments give rise to the paired mesodermal 

 oviducts in the female; in the male they form, together with the strands 

 of the ninth abdominal segment, the paired vas deferens. The ampullae 

 also eventually disappear in the female; the pair belonging to the eighth, 

 though, lasts longest, apparently not taking part in the formation of the 

 end portion of the paired oviducts. The acquisition of a lumen in the 

 entire mesoderm portion of the oviduct is a postembryonic development. 



In the male the definitive genital opening lies in the intersegmental 

 region between the ninth and tenth abdominal sterna, the former con- 

 stituting the subgenital plate. The tenth abdominal appendages shift 

 forward and fuse with the ninth, and together they form the aedeagus, 

 the ejaculatory duct, and associated structures. The ampullae of the 



