372 



THE DEVELOPMENT OF CESTODES. 



. 



FIG. 217. Scdece* : A from the intestine of 

 Sepia (after van Beneden) ; B from Lophius 



(x about 30.) 



one, and ultimately become forms, which were formerly like the Tetra- 

 rhynchi, ranked among the Bothriocephali, but since the time of 



van Beneden have been more 

 correctly described as Phyllo- 

 lothria (in the widest sense of 

 the word). The adult worms 

 live, like the Tetrarhynchi, 

 principally in rays and sharks. 

 Thus I think I am now 

 entitled to regard these Scoleccs 

 as structures parallel with 

 the wandering Tetrarhynchus- 

 heads ; and this all the more 

 decidedly since they not only 

 live in a wandering state in 



,.~. i /i ., 



y ery different animals (besides 



fishes, in Cephalopoda, snails, and 

 Ctenophora), but are also frequently observed swimming about in a free 

 state. 1 In the frequent possession of eye-spots, we might even see an 

 arrangement which specially adapts these animals for active wandering. 



The parallel would be perfect if we could show that these Scoleces 

 originated, like the Tetrarhynchus-hends, in the interior of a bladder. 



And indeed it cannot be doubted, after the observations of van 

 Beneden, that there are Phyllobothria, which pass through a Cysticer- 

 coid larval state (Phyllobothrium lactuca and Acanthobothrium coro- 

 natum)* But it appears as if these observations referred only to 

 such Cestodes as retain their early state until they are transferred 

 to their final host. At any rate the forms observed by van Beneden 

 exhibit even as bladder-worms in the appearance of their suckers a 

 very close approximation to the subsequent state. A similar structure 

 is found in a Cysticercoid of a Phyllobothrium (Echeneibothrium T) 

 which Wagener found in the large intestine of a Trygon. " Like a 

 Tetrarhynchus, the animal was suspended by threads in a sac within 

 its caudal bladder. Its head had hairs and its neck red spots. The 

 bladder was burst by pressure and the animal was set free. There 



1 Claparede twice fished a Scoltx of this sort out of the sea, and quite correctly con- 

 cluded that a "normal migration" occurred, (" Beobacht. iiber Anatomie u. Entwicke- 

 lungsgesch. wirbellose Thiere," p. 14, 1863.) The animals possessed four suckers with 

 double cups (Bothria bilocularia), and swam by a snake-like motion of the whole body. 

 Panceri found a similar Scoltx on the skin of Brama Raji (" Rendiconto Accad. Napoli, 

 February 1868). 



a With this ought to be ranked Rudolphi's Cysticercus ddphini, which was till lately 

 referred to the Cysticerci proper ; see P. J. van Beneden, Bullet, acad. roy, elg., t. xxix., 

 p. 360, 1870. 



