TF 





- x^ioai 



F 



_ ^^4¥4J^ 



GCls 



Fig. 3. — Development of the gonads and the genital ducts of insects. 



A, cross section through an abdominal coelomic sac of Blattella gcrmanica 

 (from Heymons, 1892), showing group of germ cells (GCls) in splanchnic wall 

 of mesoderm. 



B, section through posterior end of embryo of Conocephalus (from Wheeler, 

 1893), showing termination of male genital ducts in ampullae (e) in appendages 

 (XApd) of tenth segment. 



C, differentiation of female gonad of Blattella into ovarioles (from Heymons, 

 1892). 



D, showing branching of the gonadial duct (c, d) in embryo of Forficula to 

 seventh and tenth segments (from Heymons, 1895). 



E, section through a coelomic sac of Leptinotarsa (from Wheeler, 1889), show- 

 ing embryonic gonad differentiated into a dorsal suspensorium (o) attached to 

 splanchnopleure (IMsd), a germinal region (Grm), and a ventral strand (b) 

 continuous with the duct. 



F, later stage in development of female gonad of Blattella (from Heymons, 

 1892), with dorsal suspensorium (a) differentiated into terminal filaments (TF), 

 germ cells (GCls) in undivided middle part, and ventral strand (b) continuous 

 with duct (Odl). 



G, subsequent stage in development of ovary of Blattella (from Heymons, 

 1892), with gonad completely divided into ovarioles (Ovl). 



