DISTRIBUTION OF CLINOSTOMUM MARGINATUM. 357 



Wurme um sich erzeugt wurde, und in dieser liegt eingerollt 

 und zusammengeschlagen das Thier selbst." As to this inner 

 lining found by Looss no traces of it are found in my material, 

 and the cyst is wholly a product of activities on the part of the 

 host tissues. The cyst may be looked upon as a defense made 

 by the host against the parasite. It would be interesting to know 

 the nature of the stimuli which have caused this reaction on the 

 part of the supporting tissues of the muscle whether they are 

 merely mechanical and acting in the form of pressure or whether 

 they are chemical or both. The excessive formation of connec- 

 tive tissue and the growth of a definite and extensive capillary 

 network have resulted from the presence of the worm. In the 

 somewhat analogous case of the cavities produced in oak leaves 

 by the sting of certain hymenoptera for the purpose of housing 

 their larvae, the normal growth of the leaf is turned aside suffici- 

 ently to produce cavities for the larva, walled with a material 

 produced by the leaf from its own substance. In that case the 

 stimulus would seem to be chemical. Whether it is so in this 

 case cannot be determined until we are in possession of more 

 facts connected with the introduction of the parasite to the tissue 

 of the fish. 



In the bass, as already stated, the worm entirely fills the cavity 

 of the cyst. In order to determine its position within, several 

 fixed and hardened cysts were carefully dissected out of their 

 place in the muscle and the wall carefully removed under a dis- 

 secting microscope. The worms thus found bent and cramped 

 within were macerated for an hour or less in tepid water till they 

 became flexible and could be uncoiled as shown on Fig. 5. They 

 were thus found to be bent twice, both times with the ventral 

 surface outward, first on the level of the meeting of the first and 

 second body thirds, and again on the level of the second and third 

 body thirds. The first of the bends is in the median plane of 

 the body and brings the dorsal surfaces in contact; the ventral 

 sucker is thus exposed and serves to identify the surface posi- 

 ively. In making the second bend the body does not bend 

 dorsally at once but first there is a twist which brings the dorsal 

 side over the edges of the first and second thirds of the body 

 and then the dorsal surface of the last body third lap^ over these 



