OF INSECTS. 
191 
canal a considerable way beyond the extremity of the 
body. 
In the male the principal internal generative organs 
are the testes, vasa defer eiitia, vesicula seminalis , and 
ductus ejaculatorius : the external are the penis, and 
the prekensory organs connected with it. 
Like the majority of the secreting vessels in in- 
sects, the testes are commonly slender and convoluted, 
and they occupy nearly the same portion of the ab- 
domen as the ovaries in the opposite sex. Some- 
times there exists only one globular body, as is found 
to be the case among the diurnal and crepuscular 
Lepidoptera ; frequently a pair, and not rarely four 
separate ones varying in size. In their forms and 
disposition they vary almost without end in different 
groups. The ducts by which they are united to the 
common 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- 
der, which is the vesicula seminalis. The size of 
the latter generally bears some proportion to that of 
the testes, and in not a few cases it appears to be 
wanting. 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- 
