ENTOZOA. 77 



infested by the B. auriculatus is a carnivorous fish {Mtcstehcs vul' 

 garis), inhabiting the same sea as the Eledo7ie moschata, and prone 

 to devour that and other kinds of cuttle-fishes. The fertile ova of 

 the B. auriculatus are discharged by thousands from the molluski- 

 vorous fish, and thousands of the larvae doubtless perish. Some, 

 however, gain an entry into the interior of the lower organised 

 marine animals suited to their further development and encysted 

 life ; still fewer complete their vital career when the, to them, lucky 

 accident occurs of the devouring of the mollusk containing them by 

 the fish whose intestines form a suitable nidus for their ultimate 

 transformation, and for the development and propagation by spon- 

 taneous fission of the generative segments. 



Another cestoid larva found in cuttle-fishes and other marine 

 invertebrata is characterised by its four lateral elliptical suckers, the 

 tumid borders of which are facetted, or divided by many incisions. 

 The Botliriocephalus coronatus, " bothriis tumidulis transversim 

 costatis," of Rudolphi, presents the like peculiarities of its suckers, 

 and it is found in the intestines of fishes that feed upon the inverte- 

 brates and smaller fishes in which the larva in question (Scolex 

 poh/morphus, Auct.*) is found. 



To take a final instance, indicative of the migration of the cestoid 

 larvae, from land animals. The common tapeworm of the cat, 

 Taenia crassicollis, is remarkable for the disproportionate size of the 

 head, the short and thick neck, the position of the four suckers, and 

 the shape and number of the booklets of the uncinated proboscis : all 

 these peculiarities are repeated in the larval form of tape-worm 

 which is commonly developed in cysts of the liver of the mouse and 

 rat, and which has ali'eady been described as the Cysticercus fascio- 

 laris. The warm blood and high organisation of the small mammal 

 in which that larva is developed may well be regarded as favouring 

 a further advance of that development than takes place in the en- 

 cysted cestoid larvjE found in the cold-blooded invertebrates ; and 

 accordingly we find, not only the uncinated proboscis and suckers of 

 the tapeworm established, but also a lengthening and segmentation 

 of the body, in the so-called Cysticercus of the rat, without, how- 

 ever, the development of the generative organs, and with a tendency 

 to a dropsical accumulation of nutrient fluid in a few of the terminal 

 joints. 



All cestoid larvae which find their early entrance into the soft tissues 



* LI. t. xi. fig. 10. The cestoid lanrc, in their various grades of development, 

 have served as the grounds of many nominal genera of entozoa ; e. g. Anthoce- 

 phalus, Balanophorus, Bothriocephahis bicolor, Dibothriorhynchus, Floriceps, Gymno- 

 rhynchus, Hepatoxylon, Bhynchobothrium, Scolex, Tentacularia, and Tetrarhynchv.t. 



