206 ANATOB1Y. 



by degrees or at one spot, unite into one common duct. The first case 

 is found only in the compound capitate testes ( T. cap. compositi), but 

 universally here. Thus the twelve ducts of the twelve glandular 

 bodies of Celonia aurata unite by degrees to a common sperm duct ; 

 indeed some of them previously unite together before they empty 

 themselves into the common duct. In Prionus (PI. XXIX. f. 19.) the 

 single ducts empty themselves alternately into the end of the common 

 sperm duct ; the same in Cicada, Latr., in which each branch bears 

 several glands. The second connection of the sperm duct is peculiar 

 to the verticillate testes : here all the single sperm ducts unite at the 

 end of the common duct, consequently at one spot. It is similar in the 

 double testes (!T. cap. gemini), where consequently the sperm duct 

 furcates at its extremity ; the same in Blaps, where two equal branches 

 are found, each bearing a testis, and then a third, longer originating 

 from the fork, which, however, bears no testis. The length of the 

 sperm ducts is subject to no less variety. They are short in all those 

 instances where they do not exceed the length of the abdomen, and, 

 consequently, make no convolutions, as for example, in Lucanus, 

 Hydrophilus, Locusta, Callichroma, Libellula, Nepa, and, in general, 

 where there are large testes ; moderately long, that is, from twice to 

 three times the length of the abdomen, they are found in those instances 

 in which the different appendages we are about to describe are wanting, 

 for example, in Semblis, Sialis, Phryganea, and Cercopis ; long or 

 very long in those testes which are smaller and composed of several 

 bodies, or in general of a convoluted canal, for example, in Dyticus, in 

 which they are about five times as long as the body, and, like the 

 testes, convolute themselves into a small knot (PI. XXIX. f. 7- b.) ; 

 then in Necrophorus and Blaps eight or ten times as long ; in Cicada, 

 Lat. fourteen times as long ; and in Cetonia aurata, nearly thirty 

 times as long. A short but very broad and indeed gradually distending 

 sperm duct is found in Meloe and Lytta (PI. XXIX. f. 17. b.), whilst 

 in other cases it maintains a uniform compass. 



The sperm bladder has generally a more muscular structure than 

 the sperm duct. The size is proportionate to that of the testes, and is 

 wholly wanting to the less compact sexual organs, where the narrow 

 sperm duct passes into the common ductus ejaculatorius without any 

 distension. It is wanting, for example, in the Carabodea and Hydro- 

 canlharides, in Lucanus, the Capricorn beetles, all Lepidoptera, 

 Libellula, Ccrcopis, and several others ; as a slight distension at the 



