The outer integument is white, translucent, highly elastic and exten- sible, and marked with regular fine transverse or circular rugæ which cannot be satisfactorily referred to the existence of circular fibres. The membrane is composed of several laminae of a fibrous texture, and the fibres composing these laminae appear to be so arranged as to de- cussate each other in the alternate laminae. The internal membrane or tube constituting the body of the worm is constituted of a delicate pulpy substance thrown into rounded folds or processes hanging as it were into the cavity or towards the axis of the animal. The pulpy substance constituting these processes is studded with numerous bright irregularly globular particles. Between the outer and inner tubes, runs on opposite sides of the worm, a long band of muscle which is continuous from one end to the other, and the fibres consti- tuting these bands are not marked with transverse striae. On each side of either of these muscular bands is a narrow tract of a substance of minutely granular aspect, and having down its centre what appears to be a slender channel or tube without distinct walls. It was hinted that these granular tracts were of the nature of nerves, no other trace of which, could at all events be observed. The cavity of the worm circumscribed by the lobular folds above described, is occupied by a grumous or pultaceous matter, in which the innumerable young are imbedded in greater or less proportion. In some worms or in some parts of them occupying the whole space, whilst in other instances the grumous matter predominates, and only a few young Filariae are here and there observed imbedded in it.
Through this cavity also runs a narrow brownish coloured intestine, simple and straight, consisting of a delicate transparent membranous tube, and containing a brownish granular material. This intestine terminates near the caudal extremity of the worm in a pointed cœcal end.
The young Filariæ differ considerably in their outward form from the parent worm, being furnished with a long, tapering tail, which con- stitutes about two-fifths of the length of the body. The whole length of the young one being about one-fortieth of an inch. The anterior extremity is rounded, and exhibits a minute aperture, leading into what appears at first sight, a simple ventricular cavity, but which un- der particular circumstances is seen to be folded or convoluted. No trace of muscular bands nor of any separate intestinal tube can be ob- served in the young Filariæ. The young are very nearly of uniform size and appearance in all parts of the parent worm, but occasionally one less developed than the rest is met with. Intermixed with the
