53 



integument, (fig. 5), which appears smooth to the naked eye, is found 

 when examined under the microscope, to be granulated all over with 

 minute dentiform or pointed processes, which appear to be of a harder 

 nature than the rest of the tegument, and resemble on a small scale 

 the spinous prominences in the tegument of certain cartilaginous 

 fishes, as the sturgeon ; and it appears to be only an extraordinary 

 development of these latter processes which constitutes the long fea- 

 thery lateral appendages already described. 



The mouth of this larva is perhaps the most interesting part of its 

 anatomy. The head (fig! 6) is furnished with two broad fleshy lips, 

 (a a) which together constitute a broad disk, having in its centre a 

 minute aperture {b) leading to the oesophagus, and flanked on either 

 side by the hook-shaped mandibles, the sharp points of w r hich are 

 directed downwards and somewhat outwards, {c c) and are nearly re- 

 tracted each within a separate sheath, the aperture in the extremity 

 of which just allows their points to protrude. Each of these broad 

 fleshy lips is crossed by transverse parallel plaits or folds of mem- 

 brane, about twenty-five in number, which in their free margin exhibit 

 a delicately notched appearance, and in fact in every particular re- 

 semble a similar structure which is seen on a larger scale in the 

 sucking disk situated upon the dorsum of the head of the Remora. 

 by w r hich that fish is enabled to attach itself firmly to various objects. 

 In the present instance, however, the structure, though precisely simi- 

 lar, is exceedingly delicate, and so minute as to be invisible to the 

 naked eye, though there can be no doubt that it is intended to answer 

 the same purpose in both. For by the aid of this sucker the larva is 

 enabled to fix the head, so as the more readily to insert its sharp 

 hook-shaped mandibles into the soft mucous membrane of the intes- 

 tine which it inhabits, and draw therefrom its nutrient juices, which 

 w r ould thus readily flow into the little aperture of the mouth, situated 

 in the centre between the mandibles, assisted also by the partial va- 

 cuum which would thus be produced during the act of adhesion. 



The mandibles are sunk so deep between the two fleshy lips, having 

 only the points projecting from the aperture of their investing sheaths, 

 that it is necessary to disconnect them entirely from the soft parts be- 

 fore they can be accurately examined. They are placed parallel to 

 each other, with their hooked points directed downwards, so as the 

 more readily to be inserted. The mandibular apparatus (fig. 7, a, and 

 fig. 8) on each side consists of three portions. The first portion is 

 hooked and sharp pointed, (fig. 8, a) and is only the -^ of an inch in 

 length. It is nevertheless furnished at its base with a delicately 



