414 



ORGANS OF GENERATION. 



cavity, immersed in the juices of the body, 

 from which they derive their secretion. Never- 

 theless, although essentially constructed upon 

 similar principles, the testicular coeca present a 

 singular diversity of form in different genera, 

 and some of the modifications are sufficiently 

 curious, although in the present state of our 

 knowledge it would be hopeless to attempt to 

 explain the reason of their existence. Miiller, 

 from a comparison of the researches of various 

 authors upon this subject, has given the follow- 

 ing summary of the principal forms of the 

 sperm-secreting organs, and although the cata- 

 logue of varieties might doubtless be considera- 

 bly extended, those given will abundantly an- 

 swer our present purpose. Beginning from the 

 tubular vessel, which is the simplest form of 

 the testis, he traces it through the various com- 

 plications here enumerated. 



1. Simple tubes not branched, but more or 



less convoluted and closed at one extre- 

 mity. 



2. Spiral tubes similarly closed, as in Spho- 



drus terricola. 



3. Spiral tubes rolled up into little balls, as 



in Carabus auratus, Aptinus duplotor, 

 Dytiscus, &c. 



4. Simple tubes irregularly branched, each 



branch vesicular near its extremity, as 

 in Prionus coriarius. 



5. Simple tubes, divided in a verticillate 



manner, each division being terminated 

 by a capsule ; Searabaut nasicornis, 

 (Swammerdam.) 



6. Simple tubes, divided as the last, but 



each division ending in a vesicle, as in 

 Trich iusfasciatus. 



7. Simple tubes ending in stellated capsules, 



the apices of which are produced into 

 slender tubes; Nepa cinerca, (Swam- 

 merdam.) 



8. Simple tubes giving off a series of canals, 



each of which is terminated by a disc- 

 shaped capsule ; Cetonia uurata. 



9. Simple tubes, ending in flower-shaped 



capsules, i. e. each capsule consisting 

 of a central vesicle, with other smaller 

 ones placed around it, as in Asida gigas, 

 (Edemera calcaratu, Diaperis violacea, 

 Tenebrio obscurus, (Edemera carulea, 

 &c. 



10. Simple tubes, each terminated by a trans- 



verse capsule, resembling the anther of 

 a flower, as in Apis, Bombyjc, Scaris, 

 Calvinia, Sac. 



11. Simple tubes, dividing into minute radia- 



ting utricles ; Bostrichus capucinus. 



12. Simple tubes, each terminated by a cap- 



sule, which is covered externally with 

 innumerable little vesicles or utricles, as 

 in Musca asilus, Elater murinus, Blaps 

 g'gtts, Telephones J'uscus. 



13. Simple tubes, ending in an elongated sac- 



culus,to the sides of which are appended 

 small vesicles arranged in longitudinal 

 rows, as in Semblis bicuuduta. 



14. Simple lubes terminating in verticillate 



utricles, as in Clerus ulveolarins. 

 15. Simple tubes, from which arise utricles 



18. 



19. 



Fig. 202. 



arranged like the teeth of a comb, as in 

 HydrophUw piceus. 



16. Simple tubes, terminated by a simple sac- 



culus ; Gyrinus natutor. 



17. Simple tubes, terminated by a bunch of 



vesicles. 



Simple tubes, dividing into minute canals, 

 forming a kind of cauda equina ; Tri- 

 chodes apiarius. 



Branched tubes, each branch being termi- 

 nated by a vesicle, as in Staphilinus 

 maxillosits. ( Fig. 202 .) 



20. Tubes very much branched, some of the 



ramusculi ending in bunches of leaf- 

 like utricles, others dilating into pe- 

 dunculated vesicles ; Sulpha obscura. 

 (Fig. 203.) 



21. Simple loculated utricles, as in Ephe- 



mera. 



It is manifest from this sur- 

 vey that, although the secern- 

 ing organs differ so much in 

 form, the canals composing 

 them invariably terminate in 

 blind extremities ; nor is it 

 less obvious that the nature 

 of the testis does not depend 

 upon any peculiar arrange- 

 ment of the seminal tubes, but 

 upon the increase of surface 

 obtained by the various ar- 

 rangement of the vessels. Se- 

 cretion, therefore, here, as in 

 every other case, is effected by 

 the internal surface of tubes, 

 utricles, sacculi, &c. the same 

 end being accomplished in 

 some cases by means of very 

 long simple canals, which in 

 others is effected by smaller Testicle of Staphy. 

 branches, tubes, or agglome- linus maxillosus. 

 rated vesicles. 



Fig. 203. 



Testicle of Silpha obscura. 



Appended to the excretory ducts of the testi- 

 cular organs, near their termination, is found a 

 group of ccecal tubes, evidently destined to 

 provide an accessory secretion; these have been 

 named from analogy vesicula scminales. They 



