Loxogenes arcanum Nickeeson. 273 



was composed of a very thick dense material, which bore con- 

 siderable resemblance to that of the wall of the small intestine. 

 Unfortunately these cysts were not preserved, so that it is not 

 possible to determine their exact histological structure, but their 

 position upon the intestinal wall and the resemblance in texture of 

 their wall to that of the intestine, makes it seem very probable 

 that they originated as saccular outgrowths of the substance of the 

 wall of the intestine, formed for the purpose of lodging the worms, and 

 that these had become more and more completely closed off from the 

 cavity of the intestine and finally had separated from it altogether 

 and drifted off into the mesentery. A careful examination was made 

 to determine whether any connection still existed between the lumen 

 of the intestine and the cavity of the large cyst, which still remained 

 in intimate connection with the wall, but none could be found. All 

 the cysts were entirely closed. Nickeeson reported that he found 

 the same thing in the specimens from Massachusetts which he 

 examined. 



In marked contrast with this is the fact that all the European 

 members of the Pleurogenetinae inhabit the intestinal cavity of 

 frogs, so that they are all free living forms, while all the American 

 members of the group have lost the free habit and live in en- 

 cystment. It is quite remarkable and unusual to find a mature 

 trematode living in encystment, indeed I do not now recall another 

 case of this, either in the Trematodes or in the Cestodes. The 

 meaning of this habit of Loxogenes is quite obscure. Encystment, 

 a very frequent habit in this group, is usually adopted by the im- 

 mature worm as a means of reaching a later host from a more 

 primary one. But in this case the worm is mature, the coils of its 

 uterus are filled with eggs, and eggs are found floating about freely 

 in the cavity of the cyst. It would therefore seem as if the en- 

 cystment would prevent the eggs from finding the host necessary 

 for their development and it is difficult to imagine any way in 

 which the encystment is advantageous to the worm. 



II. Movements of the liberated worm. 



The living worm has a light creamy ground color on which the 

 vitellarian follicles are seen anteriorly as dead white spots and 

 more posteriorly some of the coils of the uterus are discernable as 

 very dark brown almost black elongate masses, clustered on the 

 right and left sides. In a living specimen, examined under very 



