166 THE COCKROACH 



From this ganglion a median recurrent nerve runs 

 backwards on the oesophagus, beneath the supra- 

 cesophageal ganglia, from which it receives a pair 

 of ganglionated 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 backwards over the surface of the crop. 



E. Sense Organs. 



1. The tactile organs have been already 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 fenestrae are possibly sense organs, but their func- 



tion is unknown. 



F. The Eeproductive 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 vesiculae seminales. 



c. The vesiculae seminales, or ' mushroom-shaped gland,' 



are two tufts of white glandular caeca, 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 



