PARASITES. 383 



be said to have something in common with royalty of the 

 olden date, 



" Upon whose spirit, depend and rest 

 The lives of many." 



The parasites of the marine bivalves, and of the marine 

 Mollusca in general, have been scarcely indicated,* if we 

 except an entozoon (Vertumnus tethydicola) that sucks to 

 atrophy the beautiful Tethys, f and some that infest the 

 Cephalopods. Delle Chiaie enumerates an Ascaris, a Filaria, 

 a Scolex, a Cysticercus, a Monostoma, a Distoma, a Bothrio- 

 cephalus, and a Dibothriorhyncus amongst the parasites of 

 the latter class ; J and a peculiar species is devoted to the 

 Argonaute. One of the most wonderful entozoa hitherto 

 described is the leech-like worm, named by Cuvier Hecato- 

 stoma or Hecatacotyles, because of its having a hundred cups 

 and upwards for attaching itself to its peculiar victim the 

 Octopus granulatus, one of the Cephalopods of the Mediter- 

 ranean. This parasite " lives in the abdominal cavity, or even 

 in the substance of the flesh of the polypus, the only ani- 

 mal which surpasses it in the number of cups with which 

 it is furnished. M. Cuvier remarks how favourable this 

 circumstance is to the metaphysicians who amuse themselves 

 with composing the intestinal worms all of a piece with the 

 elements furnished by the body of the animals which they 

 inhabit. Here we have the body of a polypus, which has 

 for its parasite a worm, so like the arm of a polypus, that 

 the illusion cannot be greater. Of the two polypi which 

 he produced before the Academy, there was one in which 

 the Hexacotyles was attached to one of the arms, which 

 it had even nearly destroyed, and which it seems in such a 

 degree to replace, that at first sight it might be taken for 

 the arm itself. * Let it be judged,' said M. Cuvier, * how 

 many theories might be founded on such an extraordinary 

 resemblance. Never has the imagination been exercised 

 on so curious a subject.' "|| I take my leave of it in the 



* In his Entozoorum Synopsis, Berolini, 1819, Rudolphi does not men- 

 tion a single species parasitical on these Mollusca. 



t " The characteristic Nudibraric of the Mediterranean, a giant among 

 its tribe, Tethys leporina, was only met with once, swimming foot up on 

 the surface of the sea in the Gulf of Smyrna in an exhausted state, its 

 sides being invested by that extraordinary parasite the Vertumnus tethy- 

 dicola." E. FORBES in Report Brit. Assoc. 1843, p. 133. 



J Anim. s. Vert. Nap. iv. 61 : 200, 201. 



Tricocephalus acetabularis. D. Chiaie, lib. cit. ii. 225. 



|| Edinb. New Phil. Journ. Jan. 1830, p. 102. Edinb. Journ. of Science, 

 i. 219. 



