316 ItnE Microscope. 



an interesting paragraph appears in the last annual report of 

 Secretary Noble, of the Interior Department. The waters of 

 the Yellowstone region were visited recently by Prof. Edwin 

 Linton, who, in conjunction with Prof. S. A. Forbes, has reported 

 informally concerning the probable nature of the trout parasite. 

 These investigators believe that the parasite will be found to be 

 a larval, or immature and non-sexual, form of animal life, resem- 

 bling the " measles " stage of Taenia solium in the swine. In 

 other words, this trout parasite is an example of that order ©f 

 worms which complete the cycle of their life in two different 

 animals. Having this hypothesis in view. Prof. Linton began a 

 search for some form of animal which, by feeding upon the trout 

 in a raw condition, would be likely to become the host of a sex- 

 ually mature intestinal worm corresponding to the cystic and 

 larval stage observed in the trout. He examined a number of 

 the fish-eating birds occurring in the vicinity of the Yellowstone 

 Lake, and finally hit upon the pelican as the probable final host 

 in this alternation of generation. The pelican was found to have 

 an intestinal parasite which had eggs and which appeared to 

 belong to the same genus as the form in the trout. Collateral 

 proof was obtained by opening the stemachs of some of these 

 birds and finding therein ingesta of trout. These birds, four in 

 number, were shot at Molly Island, in the southerly part of the 

 lake, a favorite breeding-place to which the birds resort in great 

 numbers. The pelican is, moreover, the only fish-eating bird 

 that occurs on the lake in large numbers. It is understood that 

 this bird consumes the fish of every description that happens to 

 be left dead on the shores of the lake. The worm-infested trout 

 is believed to be confined to a very limited and well-defined 

 region of the waters. Mr. Linton's research was conducted with 

 only an imperfect suppl}^ of appliances, and he expects to make 

 a more careful examination of the materials he was able to col- 

 lect and bring home. 



Appropriate to this item is the fact that it was reported some 

 months since that the trout of Loch Katrine, in Scotland, were 

 infested with the tape-worm parasite or larva, and a certain 

 amount of " scare " was created in the district which takes its 

 drinking-water from that Loch, lest the citi^.ens should serve as 

 the unwilling host for maturing the incomplete taenia, and lest 

 an " epidemic " of tape-worm might occur. Our impression is 



