i.ENITAL ORGAN*. 



343 



A 



Fig. ICO.— Transverse section through the abdomen in three consecutive stages of develop- 

 ment of Phyllodromia germanica (after Heymoks). am, amnion; hg, rudiment of the 

 ventral chain of ganglia; c, coelomic cavity; c', dorsal, and c", ventral sections of the 

 coelomic sac; i ■:, cells of the wall of the primitive segments, applied to the ventral side 

 of the genital rudiment; d, food-yolk ; dw, dorsal wall of the coelomic sac; cc, ectoderm ; 

 ep, epithelial cells ; ex, abdominal limb-rudiments ; /, rudiment of the fat-body ; gz, genital 

 cells; Iw, lateral wall of the coelomic sac; m, mesoderm-cells, which do not take part in 

 the formation of the coelomic sacs ; mw, median wall of the coelomic sac ; so, somatic 

 mesoderm-layer ; vm, ventral longitudinal muscle. 



