The development of the ovary in the grasshopper, Melanoplus differentialis (acrididae; orthoptera)

Each indifferent genital rudiment in the grasshopper embryo is composed of the following: (1) a terminal filament membrane; (2) an epithelial plate of indifferent cells, the dorsal cell mass; (3) the central cell mass containing germ and indifferent cells; (4) the ventral cell strand, and, (5) a delicate, investing membrane, the outer limiting membrane. It is roughly spindle‐shaped in transverse section and extends from the first to the eighth abdominal segments. In the sexual differentiation of the genital rudiment the dorsal cell mass is retained as a definite embryonic rudiment in the female, but becomes an indistinguishable part of the central cell mass in the male. Ovarian development is initiated in the dorsal cell mass area, where cell aggregations are formed. Each aggregation is ultimately surrounded by the ingrowing outer limiting membrane to form distinct cellular columns. A latero‐ventrad extension of this ingrowing process into the central cell mass continues the column formation process into the latter and results in the formation of a distally tapering structure composed of indifferent cells distad and germ cells and indifferent cells proximad. This structure constitutes the rudimentary ovariole which finally differentiates to form the terminal filament, germarium, and vitellarium. The ovarian portion of the oviduct and the tubular connection between the ovariole and oviduct are differentiated from the ventral cell strand.