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Notice of a curious Aquatic Larva, found in a Water Jag at Twizell, 6th 

 March, 1839. By P. J. Selby, Esq. of Twizell-House. 



In length, it measures about three lines, and is of a peculiar shape, 

 being anteriorly slender, and bidging posteriorly into an oval or flask- 

 shape. The posterior extremity is furnished with a small central 

 sucker, and three lateral fleshy protuberances, which also act as suck- 

 ers, and by means of which it adheres to the glass or sides of any 

 vessel in which it is placed ; it also possesses two fleshy tubercles or 

 pro-legs on the convex surface of the first segment ; and its mode of 

 progression is something similar to that of the geometrical caterpillars, 

 as, when wanting to change its situation, it extends its body to its full 

 length, and then &xes its anterior legs, after which it draws up the 

 hinder part of its body to where they are placed, and securing itself 

 by the suckers, thus advances by alternate movements, each step 

 covering a space nearly the length of the whole body. The head is 

 of a square form and large, and the eyes, which are black, are situ- 

 ated towards the margin of the hinder angle. On the forehead, two 

 pellucid bristle-like antennae are visible, and the mouth is furnished 

 with a curious apparatus, the parts of which, however, are too small 

 and delicate to be distinctly made out, without the aid of the micros- 

 cope. Under a considerable power, these parts exhibit a beautiful 

 and highly-curious conformation ; but are admirably adapted to its 

 mode of life and predacious habits in this its larva state. To convey 

 an accurate idea of these cibarian instruments by verbal description, is 

 almost impossible ; for, to be properly understood, they ought to be 

 seen in action, and under the power of a high magnifier. The 

 following description, however, may serve to give some general 

 notion of their structure and mode of action : — On each side of the 

 superior part of the mouth, and below the insertion of the antennse, 

 an instrument (which I take to be one of the palpi), of extraordinary 

 configuration, and which, when fully developed, and the animal is 

 engaged in search of prey, projects to a distance on each side of 

 the head or face : the basal part of this instrument is composed of 

 a large and powerful clavate-shaped joint, the apex of a number 

 of bristles, or rather fine laminae, which diverge or open like a fan ; 

 only, that being bent, they form, when thus expanded, a concave 

 or hollow trap. These vibrissse, — except in so far aa the whole 

 of the apparatus can be opened or shut, or placed in a state of 

 rest over the mouth, — possess no vibratory motion, nor do they 

 appear to be furnished with ciliee ; but to produce a current, and 

 bring the animalcule upon which the larva feeds within the vortex 

 of this curious and delicate trap, two other members of the mouth, 

 and which I consider to be the mandibles, are constantly engaged 

 in alternately catching at a small projection, which is placed 



