OF THE CYSTIC ENTOZOA. 99 



closely covered with short slightly curved spines, directed back- 

 wards. These spines are largest round the suctorial mouth, and 

 on the posterior part of the body are gradually replaced by mi- 

 nute tubercles or dots. Under this spiny or cuticular layer, the 

 integument is muscular, the fibres being principally transverse, 

 and so arranged that the animal appears to be made up of a series 

 of rings, as may be observed along its edges, when examined by 

 transmitted light. 



From the anterior extremity to the acetabulum the integu- 

 ments are so opaque, from the dense covering of spines, that the 

 internal structure of the animal cannot be detected. It is pro- 

 bable, however, that the oesophagus terminates as in the family 

 Distoma generally, in two blind intestinal tubes. I have failed 

 in detecting an arrangement of this kind ; but I have observed 

 about the middle of the animal, and along the sides of its posterior 

 half, a sort of cellular structure, which may probably belong to 

 the digestive system, as in Distoma clavatum described by Pro- 

 fessor Owen.* 



A large sac, evidently connected with the digestive system, 

 opens externally by the minute orifice, at the posterior part of 

 the animal. This sac, in every individual, is full of a matter, 

 which by reflected light is of a chalky whiteness, and described 

 by Monro, and conjectured by him to be of a cretaceous nature. 

 Examined by transmitted light, it is seen to consist of numerous 

 spherical globules of variable size, and resembling the matter 

 which fills the chyle cells of the intestinal villi. The larger sac 

 in which this matter is contained varies in shape, but it generally 

 passes up from its outlet for about a third of the length of the 

 body of the animal, then takes an acute bend to the other side, 

 and passing forwards in a curved direction, ends in a dilated 

 blind extremity between the acetabulum and the mouth. It is 

 the " sigmoidal" or " serpentine body" of Monro. This sac is 

 evidently the " cisterna chyli." 



It does not communicate directly with the digestive system, as 

 in the apparently analogous receptacles in Distoma clavatum, nor, 

 as far as I could see, with the vascular system ; but I have seen it 



* Owen. " On the Anatomy of Ditfoma Clavatum," Trans. Roy. Soc., Vol. 1. 



