MALE ORGANS OF GENERATION. 201 



abdomen, as they occupy precisely the same place possessed by the 

 ovaries of the female, namely, the lateral spaces in the abdominal 

 cavity contiguous to the intestinal canal, yet inclining more towards 

 the venter. Those only which are united into one testis lie directly in 

 the middle of the body immediately beneath the nutrimental canal. 



With respect to their precise shape, having thus indicated their most 

 general differences, and distinguished them as tubular or vesicular, they 

 may be arranged under several chief forms with various subordinate 

 differences, which the following classification endeavours to display. 



I. SIMPLE TESTES. The long testes which, in the early stages, are 

 divided, approach more closely together in the progress of development, 

 and, lastly, in the pupa state, unite into one single globular testis, 

 (Pi. XXIX. f. 1.) the earlier separation of which is indicated by a ring 

 upon its surface. Each of the hemispheres divided by this ring has its 

 own peculiar duct, which unite afterwards together. 



This structure of the testes is peculiar to all the diurnal, crepuscular, 

 and nocturnal Lepidoptera, as well as the Pterophori ; other moths 

 (the Tinea) have them always separated. This testis consists, upon 

 closer inspection, of a thick cellular mass, which is pierced everywhere 

 by delicate ramifications of the tracheae. 



II. SEPARATED TESTES. The testes remain during the whole 

 course of the insect's life separated from each other, and lie on each 

 side of the intestinal canal. 



A. SIMPLE VASCULAR TESTES. Each testis is a simple filiform or 

 wider vessel, which lies either extended at full length, or makes convo- 

 lutions, but it sometimes is entangled in a hank. 



1. Testiculi lineares (PI. XXIX. f. 2.). They lie stretched out, 

 and are wider than the ductus ejaculatorius into which they pass by 

 means of a sudden constriction, and run upwards in a conical point. 

 (Libellula.} 



2. Testiculi clavati. (PI. XXIX. f. 3.). Each testis is an obtuse 

 club, which gradually contracts itself into the ductus ejaculatorius, and 

 thus imperceptibly passes into it. (Cercopis, Tinea.) 



3. Testiculi JUiformea. (PI. XXIX. f. 4.). The testis is a twisted 

 filament, which lies wound up in the abdomen, and, before it passes into 

 the duct, distends into a longitudinal sperm bladder, (b. Tipula.) 



4. Testiculi spir ales. (PI. XXIX. f. 5.). They distinguish them- 

 selves from the preceding merely by each filiform testis being twisted 



