519 



Nerv nus trunks. All the teil longitudinal nerves and three 

 transversal nervous rings, described by C o h n in D. laevis are also 

 found in the worm in question. In addition to thein one sees here 

 still: 1) an inner thin nerve ring, lying on the boundary of the pro- 

 glottides (fig. 19. n. n. t. in.), towards the inner transversal muscles, 

 arising from the internal or principal lateral nerve; 2) shorter similar 

 transversal nerves (fig. 16, n. gen.), which lie in the same horizontal 

 plane, but in the middle of each proglottis, near the reproductive 

 glands, and start from the middle external nervous ring, near the 

 median longitudinal nerves extending towards the interior. 



Reproductive organs. The most important différence be- 

 tween D. laevis and D. sui-generis consists in the number of the 

 testes, vasa efferentia and vasa deferentia. Whilst in the former 

 species there are only three testes, in D. sui-generis their number 

 varies from 3 to 7. The common number is 5 to 6 (fig. 12, 13, tes.). 

 A more important detail is that from each testis proceed several 

 vasa efferentia, in varions numbers, 2 to 5 (fig. 14, v. ef.). Winding 

 many times and joining one another. they form a very much com- 

 plicated net of canals, which opens into the proximal ends of both 

 vasa deferentia (fig. 14, v. def ). It is interesting to note that those 

 proglottides which do not possess the middle testis (fig. 14) contain 

 nevertheless a similar net (fig. 20, r. ef), a fact which can only 

 be explained by the supposition that the testis disappeared, leaving 

 however its vasa efferentia. 



The author considers the cells surrounding the séminal vesicle 

 (fig. 14. c. p.) as glandulär, producing an albuminoide fluid, in 

 which the Spermatozoons swim and which fills the vesicle. also the 

 second little vesicle near the circus-pouch and, in the older proglot- 

 tides, both vaçinae and the vagina communis (fig. 17). The hooks 

 upon the cirrus (fig. 15) resemble those in D. laevis according to 

 the description of Jacobi (and contra (John). In the structure of 

 the female reproductive organs there is no great différence between 

 D. laevis and D. sui-generis. The vagina communis is here however 

 not „eine kleine Erweiterung", as Coh'n says (2) in D. laevis, but 

 a large long canal, as shewn by fig. 17 (vg. e.). 



Ail the other détails in the anatomy of the tapeworm in ques- 

 tion are evident from the adjoined drawings (fig. 12 — 20) and 

 require no further expiration. 



