60 Zoological Society. 



an inch or 1| inch in thickness. From the size and colour I have 

 adopted the name of Megascolex c^ruleus. 



" The body is composed of 270 rings, the sexual organs occupying 

 the 16th, 1 7th and 18th ; between this part and the head it is some- 

 what ventricose, but at the 1 7th ring there is a decided narrowing. 

 Each ring is dilated in the middle of its length into a ridge, which 

 carries on it, except in the mesial line of the back, minute conical 

 mammillae, 100 in number, each surmounted with a minute bristle, 

 arched backwards ; the dermoid covering is striated in opposite di- 

 rections diagonally, to admit of the contractions of the muscles be- 

 neath ; dorsally the depressed parts of the rings are deep bright blue, 

 which becomes gradually narrowed as it descends the sides, and ter- 

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

 absolute ventral part is pure yellow. 



** The intestinal canal is very large, extending to within an eighth 

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

 membranous partitions, attached externally 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, which 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 works which I have examined it is stated (I think origi- 

 nally 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 whole breadth, is the orifice of the respiratory apparatus, 

 a narrow oval ; they are first visible in the interval between the 14th 

 and 15th ring, and terminate between the 17th and 18th from 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 like a reticule, with a rectangular bottom ; the sides of this 

 space are formed as follows : the muscle 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 must necessarily be more or less 

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

 mediate walls of the sac is so fine and so loose that I failed in all 

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



