^'§. 114, 115. THE HELMINTHES. 119 



CHAPTER IX. 



ORGANS OF GENERATION. 



§ 114. 



Although most of the Helminthes propagate by means of genital organs, 

 yet there are a few species which multiply by Jissuration and gemmation. 



The ^ssurafion is always transverse, and differs from that of the Proto- 

 zoa and Zoophytes in the fact that complete individuals are not produced, 

 there being only a separation of certain organs from the perfect animal, as, 

 for instance that of the segments of the body in the Cestodes. This fissu- 

 ration is complete or incomplete. In the first case, occurring in the Taenia, 

 the segments are detached from the body, and continue to live independ- 

 ently, without, however, ever forming a new individual. ''' 



Gemmation has been observed in the sexless Coenurus and Ec/tinococcus. 



In Coenurus cerebralis, it is incomplete. The buds are formed on the 

 internal surface of the parent-vesicle, and never separate from it, nor 

 become perfect individuals. They have only a head and neck which pro- 

 ject outwardly after the complete development. In Echinococcus, however, 

 the gemmation is complete. The buds appear as in Coenurus, but the 

 young animals are sooner or later detached and fall into the liquid of the 

 parent vesicle. When completely developed, this vesicle bursts, and they 

 are set at liberty. That their development occurs in this way is shown by 

 their hanging by a cord, which, like the tail of Cercaria, is inserted into a 

 fossa at the posterior extremity of the body. Like this last, also, this cord 

 subsequently disappears, and the young animal moves freely about, by the 

 aid of its double circle of hooks and its four suckers.'-^ 



§ 115. 



In those species which reproduce by male and female genital organs, these 

 last are sometimes upon a single animal, and sometimes upon two separate 

 individuals. The eggs and spermatic particles are formed after very differ- 

 ent types. In all, the copulatory organs are extraordinarily developed. 



The Cestodes and Trematodes are hermaphrodites.*'' The structure of 



1 The imperfect fissuration with Ligula and 2 See Chemnitz, De nydatibu3 Echinococoi 



Trjae«o/;Aorus is limited almost tu a constriction hominis commentatio,1834 ; MulleT,'m his Arcli. 



of tlie lateral borders. With Bothriocephalun 18o6, p. CVII. ; and Siebold, in Burdock's Phys- 



punctatus, it is only here and there that a rini< is iol. II. 1837, p. 183. 



detached, and over most of th'; body the transverse 1 According to Nordmann (Jlicrogr. Beitr. lift, 



and opposite sulcations do not extend near to the 2, p. 141), Diesing (Ann. d. 'Wiener Mus. I. 



median line. Wilh Bothriocepltaius tetrapterus, AVHh. 1, p. 9), and Miram (Nov. Act. Acad, 



the fissuration is more complete ; but even here, XVII. pt. 2, p. 636), the male and female genital 



there are only some incompletely limited rings organs of the genus Pentastomian, classed by 



among numerous others which are completely so. many modern Ilelmiuthologists among the Trema- 



Of all Helminthes the Taeniae have the most todes, are situated upon different individuals. But 



complete fissuration ; here not only is the separa- Owen affirms to have observed the opposite 



tion of the rings indicated by a complete furrow, (Trans, of the Zool. Soc. of London, 1835, I. p. 



but the rings are sometimes detached and live thus 325). The only way to settle this point is by 



independently. The separated rings of Taenia analyzing accurately the contents of these organs ; 



solium, cucumerina, and others, move freely, and a method pursued by Valentin (Kepertorium 111. 



are bo individualized, that they resemble some 1837, p. 135), who found filamentoid spermatic 



Trematodes. particles in the organs of an apparently female 



