116 



crease in size and distance from each other. They then continue of 

 the same relative size and distance apart ('2 lines) till within about 

 half an inch of the posterior extremity, when they again, however, 

 become smaller and more closely approximated. In all the four 

 specimens which I examined, the rings were twenty-seven in number, 

 and where largest, projected nearly half a line from the surface of 

 the body. 



In the fresh specimen, when examined with a pocket lens, the ex- 

 terior of the rings appeared mottled with faint white-coloured spots. 

 They wore and still are cpiite opaque, whereas the intervening tissue 

 is so thin and transparent, that the internal viscera can be seen 

 through it. A number of white bands or cords appear to connect 

 one ring with another ; the bands are largest in the lateral and dorsal 

 regions. A dark-coloured line extends along the back throughout 

 the whole length of the body : this, as I shall afterwards have 

 occasion to show, is the digestive canal. 



On the under surface, in the centre and near to the anterior margin 

 of the head, which is slightly flattened from before backwards, is a 

 round foramen, the mouth. On either side of this opening arc two 

 depressions, equidistant from each other, each containing a prehen- 

 sile hooklet of a bright yellow colour. These booklets in shape 

 closely resemble a cat's claw, which can be extended and retracted at 

 pleasure, and when completely drawn in, the points of them can be 

 neither seen nor felt. The obtuse posterior extremity has a deep 

 cleft across it, and on its under surface are two openings, one in 

 front of the other : the anterior is the entrance to the vagina, the 

 posterior the anal aperture. 



Anatomy of the Entozoon. 



Parietes. — The whole body is invested with a delicate, smooth, 

 transparent cuticle, which can be readily detached by slight mace- 

 ration. Beneath the cuticle are two layers of striated muscular 

 fibres (PI. XLVII. fig. 13), a vertical and a transverse layer; — the 

 longitudinal fibres are by far the most developed ; — the circular are 

 in some places entirely wanting. The projecting rings, on the other 

 hand, are not composed of striated muscular fibres, but consist of 

 fibro-areolar tissue. They seem to serve as fixed points of action 

 for the longitudinal muscles ; appearing to supply, in fact, the place 

 of a hard skeleton. The interior of the abdominal cavity is lined 

 by a fine transparent membrane, on which I thought I could detect 

 a single layer of delicate pavement epithelium. 



Digestive System. — The alimentary canal, in consequence of its 

 peculiar dark saffron tint, is readily traceable from its commence- 

 ment to its termination. It begins at the mouth, and runs in an 

 almost perfectly straight line to the opposite extremity of the body, 

 terminating, as was before mentioned, immediately behind the orifice 

 of the vagina (PI. XLVI. fig. 4, a). Close to its commencement 

 it is of the diameter of a fine crow-quill, and may be said to continue 

 of nearly the same size throughout its whole course. It lies directly 



