124 



EMBRYOLOGY OF INSECTS AND MYRIAPODS 



coel 



coelomic walls; but wherever they are formed, the germ cells are not 

 long retained within them but are soon thrown out into the body cavity, 



where they mature. 



The development of the repro- 

 ductive organs is, in general, the 

 same in both male and female of 

 insects having compound gonads. 

 By a multiphcation of the cells 

 along the bases of the genital ridges 

 each gonad in the female comes to 

 be suspended from the splanchno- 

 pleure by a cellular sheet (Fig. 53, 

 sus), which will develop into the 

 terminal filaments of the ovarioles 

 (Fig. 55). A thickening of the fold 

 along the lower border of the ridge 

 forms a ventral strand of the gonad 

 which gives rise to the ovariole 

 peduncles and the calyx of the 

 oviduct ; posteriorly it is continuous 

 with the free part of the lateral 

 duct. The middle part of the 

 gonad (g) between the suspensorial 

 dorsal plate and the ventral strand containing the germ cells is the 

 germarium, or the region of the primitive ovary from which are formed 

 the egg tubes of the definitive organ. 



Fig. 53." — Section through a coelomic 

 sac of Leptinotarsa. (cbl) Cardioblasts. 

 {cod) Coelom. {ect) Ectoderm, (g) Ger- 

 marium of the gonad, (nc) Nerve cord. 

 (sp) Spiracle, (splm) Splanchnopleure. 

 (sus) Suspensorium. (x) ventral strand. 

 (From Wheeler.) 



Fig. 54.— Female gonad of Blattella. 

 differentiated into terminal filaments (</). 

 (Adapted from Snodgrass.) 



X 



(gc) Germ cells, (sus) Dorsal suspensorium, 

 (x) Ventral strand continuous with duct (d). 



The germ cells at this stage, as described by Heymons in Blattella, 

 are evenly distributed throughout the length of the median part of the 

 gonad, and the organ increases in thickness owing to their multiplication. 



