90 



minates abruptly, leaving the inferior parts orange-yellow, but the 

 absolute ventral part is pure j'ellow. 



" The intestinal canal is very large, extending to within an eigbth 

 of an inch of the surface, and supported on all sides by a series of 

 membranous partitions, attached extei-nally to the edge of each ring. 

 The walls of the intestine are composed of strong but fine membrane, 

 which is separable into layers, but is without any distinct appearance 

 of fibres ; exterior to this are the muscular bundles, -vv'hich serve for 

 the progressive movements of the animal ; they are compound, 

 whitish, shining fibres, collected into longitudinal fasciculi, separated 

 by tolerably strong cellular membrane, and are deficient, as far as I 

 am aware, only in one position. 



" In all work8 which I have examined it is stated (I tbink origi- 

 nedly by Sir Everard Home) that the respiration of this tribe is car- 

 ried on through a system of pores on the sides of the animal, as in 

 the leech. This is a complete mistake ; the facts are as follows : — 

 Along the middle line of the back, as I have before noticed, the 

 mammillary projections are deficient for a space about one-tenth of an 

 inch broad, and in the interval between each ring in this situation 

 is a small transverse narrow ridge, in the centre of which, and occu- 

 pying its \vhole breadth, is the orifice of the respiratory apparatus, 

 a narrow oval ; they are first visible in the interval bet\veen the 14th 

 and 15th ring, and terminate bet\veen the 17th and ISth frora the 

 tail, being most developed at half the length of the animal, or rather 

 a little nearer the tail. The artery runs along the whole back of the 

 worm, sending ofF lateral branches at the position of the septa, and 

 at the place where the respiratory orifices open externally it forms 

 the inferior boundary of a little quadrangular space, shut up on all 

 sides by cellular membrane, so as to present the appearance of a 

 little sac hke a reticule, with a rectangular bottom ; the sides of this 

 space are formed as follows : the musele becomes deficient there, 

 taking a new attachment, and having a new origin beyond the orifice, 

 the profile being arched rather abruptly, and thus we have an ante- 

 rior and posterior wall ; the lateral are formed by the muscular bun- 

 dles of either side, and the shape mušt necessarily be more or less 

 ąuadrangular, in fact nearly square : the membrane forming the im- 

 mediate walls of the sac is so fine and so loose that I faded in aU 

 attempts to trace its form inside, but I satisfied myself of there being 

 a distinct cavity, by introducing from the outside a small blunted 

 wire, with which I gently pressed the sides ; it seemed hovvever not 

 so extensive anteriorly, posteriorly, and at the angles, as I should 

 have supposed from the form of the more solid supports outside. 



" The ręst of the anatomy of this animal I mušt leave until I can 

 procure more specimens and have more leisure. 



" When I first got the Megascolex I was sure I had obtained an 

 animal which \vould break dovvn the old division of Abranches seti- 

 geres and A. sans soies, for the bristles are so minute that I did not 

 in the first instance perceive them. As to its being a true Lumbricus 

 there could be no doubt. I was mucli gratified when I discovered 

 that the sepai-ation of the tribes, founded on a character which in- 



