THE TESTES 



495 



In his paper on the internal male organs of beetles, Escherieh states that 

 those of the Carabidae illustrate the simplest, most primitive condition (Fig. 465). 

 A simple blind tube on each side produces spermatozoa, stores the elements, 

 and secretes mucus. Each of these tubes opens into a somewhat larger duct, 

 and the two unite in a common ejaculatory canal. The terminal portion in 

 these beetles is lined with chitin, and is therefore ectodermal, and not the result 

 of the union of the mesodermic vasa deferentia. The region corresponding to 

 the testes, vasa deferentia, and seminal vesicles are mesodermic. Blaps (Fig. 

 465, B) is intermediate between the Carabidse and Hydrophilus (Fig. 465, (7). 

 The accessory glands (.<?.) are developed, and the seminal vesicles are situated 

 in the middle, and not at the lower end of the vasa deferentia, as in Hydrophilus. 



The testes. Each testis is composed of follicles or corresponding 

 parts, which according to the group of insects in which they occnr 

 are united in different ways ; or each testis consists of a single hank 

 or skein-like blind tube which is enveloped by a membrane, as in 

 the Carabidae, Dyticidse, or Lucanidse. 



The number of testicular tubes is small in most Hemiptera, but 

 very great in the Cicadidee, Orthoptera, Coleoptera, and many 

 Hymenoptera. Although the testes are usually separated from each 



-dr 



'-'ho 



FIG. 466. t, testis ; v, vas defer- 

 ens; g, seminal vesicle of Acheta 

 campeztris* After Carus, from Ge- 

 genbaur. 



FIG. 467. Male sexual apparatus of a bark-beetle : si, 

 vas deferens ; ho, testis ; bl, seminal vesicle ; dr, accessory 

 gland ; ag, ductus ejaculatorius. After Graber. 



other, they are closely united in certain Orthoptera (Gryllotalpa, 

 Ephippigera), Coleoptera (Galerucella), in many Lepidoptera, and 

 in a number of Hymenoptera (Scolia, Pompilus, Crabro, and others). 

 The two testes of most Lepidoptera are so closely grown together 

 or coalesced into a single body that one might regard them as a 

 single testis. But in the different families there occur all grades, 

 from the unpaired testes of most Lepidoptera to Hepialus with sepa- 

 rate testes. Cholodkowsky therefore distinguishes four types : 



1. The embryonal or primitive type, with two testes, whose seminal follicles 

 are entirely separate. (Brandt.) These testes are contained, as in all other 

 Lepidoptera, in a well-developed thick chitinous membrane or scrotum, analo- 

 gous to that of the higher vertebrates, which envelops each separate seminal 

 follicle (Hepialus liumuli). 



