THE CYSTIC ENTOZOA. 49 ( J 



replaced by minute tubercles or dots. Under this spiny or 

 euticular 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 

 probable, 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 Professor 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 de- 

 scribed 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 " ser- 

 pentine body " of Monro. This sac is evidently the " cisterna 

 chyli." 



It does not communicate directly with the digestive 



* Owen, "On the Anatomy of Distoma clavatum:" Trans. Boy. Soc. 

 vol. i. 



