358 HENRY LESLIE OSBORN. 



edges. The worms and cysts in the frog are very different from 

 this. They will receive attention later. 



3. BEHAVIOR OF WORMS LIBERATED FROM THE BASS CYST. 



The living worms are easily liberated artificially by cutting 

 into the cyst wall with a sharp instrument. As soon as a small 

 opening has been made the worm begins to extrude through it 

 almost as if it had been confined under some degree of pressure. 

 It continues to make active movements of extension and contrac- 

 tion which soon result in freeing it from the cyst. It continues 

 to move actively after gaining its freedom. In the course of 

 nature the worm on emerging from the fish cyst would find itself 

 in the stomach or intestine of a fish-eating bird; those which 

 \vere removed artificially were received and kept in shallow ves- 

 sels of fresh w T ater where their activities could be watched. 

 The surroundings in which they thus found themselves were 

 quite unnatural and perhaps it was for this reason that they were 

 so very active. The movements did not result in locomotion, 

 though they produced constant changes in the form of the body,, 

 but the worm did not progress. Some trematodes adhere very 

 forcibly by their suckers to any object with which they come in 

 contact but there was no attempt made on the part of these to 

 use the suckers for that purpose. Some of the various move- 

 ments were so irregular and indefinite as to preclude the possi- 

 bility of grouping them under any general head, but there were 

 others which were definite and constant enough to be classed 

 under either of two groups which I have called "poses" from the 

 fact that in each case a series of movements took place culmin- 

 ating in a certain bodily form or attitude which was only momen- 

 tarily maintained and after which the body relaxed and fell back 

 to its ordinary resting posture. These two poses were seen often 

 enough to justify the conviction that they are a constant feature 

 of the behavior of the worm and so merit a detailed description. 

 The tw r o poses will be designated the "suctorial pose" and the 

 "swimming pose." Sometimes the same pose is repeated several 

 times in succession, at other times the two alternate irregularly. 



The suctorial pose is represented in Fig. 6 as seen in the living 

 animal and in Fig. 7, a view of a sagittal section of the anterior 

 end of the body of an animal which happened to be caught in 



