.REPRODUCTION OF TJENI^. 135 



A question has often arisen in relation to the manner in which the 

 act of copulation is effected in animals presenting this remarkable 

 hermaphrodite condition of the generative system a question to which 

 Professor Van Beneden has been able to give a satisfactory solution. 

 In a specimen of PhyUobothrium luca, he had ocular demonstration that 

 the individual was self-fecundating. Its penis became unrolled, and 

 passed immediately through the vulva into the vagina, into which it 

 was deeply inserted. Active peristaltic movements of the vaginal tube 

 were very manifest, and spermatozoa were seen abundantly w in its in- 

 terior, these being subsequently conveyed by peristaltic action into the 

 copulatory pouch. The penis, after some considerable time, is with- 

 drawn, returns into its pouch, and all the organs assume their previous 

 condition. 



(347.) In studying the progressive development of the egg in the 

 Taeniae and other Cestoid worms, it is only necessary to remember that 

 all the ova contained in the same segment are of the same age, and that 

 the age of the segments increases progressively, from the head to the 

 opposite extremity of the elongated body, to enable the observer to 

 select ova in any stage of their development in order to submit them to 

 examination under the microscope. 



(348.) In their general structure, the eggs of the Taanioid Entozoa 

 are similar to those of the other classes of Invertebrate animals ; and the 

 segmentation and breaking-up of the yelk proceed exactly in the same 

 manner. 



(349.) On arriving at maturity, however, a series of phenomena of 

 the highest possible interest begin to develope themselves, which we 

 will proceed to describe with as much conciseness as the subject will 

 allow*. The worm, when it emerges from the egg, instead of being 

 composed of a series of segments, consists simply of the first segment, 

 or head, as it is called, of the compound worm, variously armed with 

 hooks, suckers, or bothria, according to the genus, to which is appended 

 a short caudal extremity, w r herein but slight traces of any internal organ 

 are apparent. In this condition it has received the name of Scolex, and 

 may be regarded as a sort of root from which all the rest of the animal 

 is developed, much in the same way as the Planulce of the Acalephse 

 are segmented off from their Hydra-like parent ( 304). In this condi- 

 tion the " Scolex " exists for some time, and in some instances, as, for 

 example, in the Tetrarhynchi, clothes itself in a kind of sheath formed by 

 a mucous exudation derived from the surface of its body. 



(350.) We have already pointed out the similarity of structure that 

 exists between the armature of the " head " of the Cysticercus (fig. 66) 

 and that of the Ta3nia (fig. 67) ; but the reader, from a comparison of 

 the two figures, would scarcely be prepared to expect that the one was 



* Vide " Recherches sur les vers Cestoides," par P. J. Van Beneden, Nouveaux 

 Mem. de 1' Academic de Bruxelles for 1850. 



