EEPEODUCTIVE SYSTEM 167 



this ganglion a median recurrent nerve runs back- 

 wards on the oesophagus, beneath the supra-oesopha- 

 geal ganglia, from which it receives a pair of gan- 

 glionated nerve-trunks : it then continues its course 

 backwards, as a median nerve, along the oesophagus 

 and crop to a small triangular ganglion on the dorsal 

 surface of the crop, about the middle of its length. 

 From this ganglion two branches run obliquely back- 

 wards over the surface of the crop. 



E. Sense Organs. 



1. The tactile organs have already been examined. They 



are the antennae, the maxillary palps, the labial palps, 

 and the anal cerci. 



2. The eyes are very large compound organs which agree 



in essential characters with those of the crayfish. 

 The corneal facets are hexagonal. 



3. The fenestrse are perhaps sense organs, but their func- 



tion is unknown. 



F. The Reproductive System. 

 1. In the male. 



a. The testes are readily recognisable in the young, 



but atrophy in the adult. They are paired organs 

 imbedded in the fat-body below the fifth and sixth 

 terga of the abdomen. 



b. The vasa deferentia are a pair of narrow tubes 



leading from the testes to the vesiculse seminales. 



c. The vesiculae seminales, together known as the 



' mushroom-shaped gland,' are two tufts of white 

 glandular cseca, opening into the slightly dilated 

 anterior end of the ejaculatory duct. 



d. The ejaculatory duct is a short muscular tube 



opening behind to the exterior, just below the 

 anus. 



e. The gonapophyses are a series of strong chitinous 



hooks and plates, forming a complex copulatory 

 organ. They are asymmetrical, and surround 

 the genital aperture. 



