OF INSECTS. 191 



lianal a considerable way beyond the extremity of the 

 [body. 



In the male the principal internal generative organs 

 lire the testes, vasa defer entia, vesicula seminalis, and 

 I \iuctus ejaculatorius : the external are the penis, and 

 \hs prehemory organs connected with it. 



Like the majority of the secreting vessels in in- 

 [jects, the testes are commonly slender and convoluted, 

 I md they occupy nearly the same portion of the ab- 

 loinen as the ovaries in the opposite sex. Some- 

 limes there exists only one globular body, as is found 

 |;o be the case among the diurnal and crepuscular 

 iLepidoptera ; frequently a pair, and not rarely four 

 [separate ones varying in size. In their forms and 

 [disposition they vary almost without end in different 

 broups. The ducts by which they are united to the 

 hommon ejaculatory duct constitute the efferential 

 vessels (vasa deferentia), which are usually slender 

 throughout the greater part of the course till they 

 become dilated into an oval or kidney-shaped blad- 

 ller, which is the vesicula seminalis. The size of 

 phe latter generally bears some proportion to that of 

 :he testes, and in not a few cases it appears to be 

 vvanting. This sperm bladder terminates in a tube, 

 joined to the corresponding one from the opposite 

 side, forming by their union the ejaculatory duct, 

 which is analogous in shape and situation to the egg 

 canal of the female. Sometimes it is short and broad, 

 at other times moderately long. The other male 

 organs mentioned above may be considered as ex- 

 ternal. The prehensile appendages are well cxem- 



