Invertebrate Gallery of the Indian Museum. 39 



to secure their hold upon the walls of these cavities the 

 Trematoda are furnished with large suckers for adhesion. 

 The intestine ends blindly. The Trematoda are represented 

 in Case 46, by specimens of Distoma hepaticum, (the com- 

 mon liver fluke), and of D. sinense^ D. crassum, and D. con- 

 junctum. In the last of these, as well as in D. sinense, 

 most of the details of the internal organization can be made 

 out through the thin transparent body-wall. 



The Flukes pass through a complicated series of larval 

 changes, or metamorphoses, in the course of their develop- 

 ment, the larval stages, like the adult, being parasitic. 



3. PLATYHELMINTHES OESTODA. 



[Silcsbm 5EitU-£a0t 46]. 



The Cestoda, or Tape-worms, are Platyhelminthes 

 that also are parasitic in the alimentary canal of vertebrate 

 animals. Mouth and intestine are alike absent, the para- 

 site being nourished by simple absorption through its soft 

 body-wall. 



A tape-worm such as Txnia solium, several good 

 specimens of which are exhibited in Case 46, consists of a 

 small head not much larger than a pin-head, followed by a 

 long chain of joints or segments, the anterior of which, 

 nearest the head, are very short, while the posterior in- 

 crease in length as they recede from the head. 



The head is the real essential part of the animal : the 

 joints, or ''proglottides" as the yare called, are to be re- 

 garded as packets of egg-cells which are constantly drop- 

 ping off at the far end as the eggs ripen, and as constantly 

 being renewed by budding immediately behind the head. 

 This explains the fact that the segments nearest the head, 

 being the latest formed and youngest, are the smallest 

 while those farthest from the head, being the oldest and 

 most mature, are the largest. 



The structure of the head is not easily seen without a 

 magnifying lens : it consists of a globular mass the apex of 



