COCKROACH. 



331 



pericardial space, and drives it forwards by a slender aorta. 

 The blood circulates, however, within ill-defined spaces in 

 the body. 



Excretory system. There are sixty or so fine (Mal- 

 pighian) tubules, which rise in six bundles from the begin- 

 ning of the ileum, and twine through the "fatty body" 

 and in the abdominal cavity. The absence of nephridia 

 in insects has been already mentioned. 



REPRODUCTIVE SYSTEM 



OF THE MALE. 



OF THE FEMALE. 



The testes are paired organs, sur- 

 rounded by the fatty body 

 below the 5th and 6th ab- 

 dominal terga. They atrophy 

 in the adult. 



From the testes, two narrow ducts 

 or vasa deferentia lead to two 

 seminal vesicles. 



These seminal vesicles (the 

 "mush room -shaped gland") 

 open into the top of the ejacu- 

 latory duct. 



This duct opens between the 9th 

 and loth sterna. Beside the 

 aperture, there are copulatory 

 structures (gonapophyses). 

 With the ejaculatory duct a 

 gland is associated. 



Large branched tubular glands 

 secrete a volatile alkaline sub- 

 stance, with a strong mousy 

 odour, probably offensive to 

 enemies. 



L 



The ovaries are paired organs, in 

 the posterior abdominal region, 

 each consisting of eight ovarian 

 tubes. These are bead-like 

 strings of ova at various stages 

 of ripeness. 



From the ovarian tubes ot each 

 side eight eggs pass at a time 

 into a short wide oviduct. 



The two oviducts unite and open 

 in a median aperture on the 

 8th abdominal sternum. Be- 

 side the aperture are hard 

 structures (gonapophyses) 

 which help in the egg-laying. 



On the 9th abdominal sternite a 

 pair of arborescent glands pour 

 out their cementing secretion 

 by two apertures. The sper- 

 matheca is a paired sac opening 

 between the 8th and the 9th 

 abdominal sternum. 



Sixteen ova, one from each ovarian tube, are usually 

 enclosed within each egg-capsule. The latter is formed 

 from the partly calcareous secretion of the arborescent 



