BULLETIN OF THE UNITED STATES FISH COMMISSION. 445 



be accounted for. Wliitefish are going to a certain extent, but they die 

 every year ou account of being driven from the cold water near the 

 mouth of the springs which supply the lake, where they congregate, into 

 the warm water which prevails everywhere else. A few pickerel also 

 are seen dead, but not enough to cause the idea of an epidemic. It is 

 the perch which get the best of fishermen now by their death. The dead 

 perch range in size from one-half pound to2 pounds. They have strewn the 

 shoie for nearly four weeks. Cart-loads are taken away and buried, but 

 still the shore is covered with their carcasses. Every gale, every breeze 

 that blows, strews them over the waves. Theories are numerous re- 

 garding this disease. One attributes it to an insect that gets into their 

 windpipe and chokes; another notices a black spot near the gill and 

 attributes to its presence the cause of which death is the effect. (Madi- 

 son Transcript, August 7, 1884.) 



S13 — DESTRUCTION OF FISII>FOO!> BV BL, ADDER WORT (Vtricularia). 



By S. A. FORBES. 



[From Forest and Stream, September 4, 1884.] 



While the very interesting fact of the destruction of young fishes by 

 the bladderwort is occupying the attention of your readers, permit me 

 to mention another method than that of direct destruction by which 

 these plants must often greatly hinder the multiplication of fishes in 

 waters infested by them. In an article on the entomostraca of Lake 

 Michigan and adjacent waters, which I published in the American Nat- 

 uralist for July, 1882, I remarked that in ten " bladders" of Utricularia 

 vulgaris, taken at random, I found ninety-tbree animals, either entire or 

 in recognizable fragments, and representing at least twenty-eight spe- 

 cies. Seventy-six of the animals found were entomostraca, and belonged 

 to twenty species. Nearly three-fourths of both individuals and si)ecies 

 were cladocera. Just one-third of all the animals found in the blad- 

 ders belonged to the single species Acroperus leueoceplialus Koch. Now, 

 my studies previously made of the food of young fishes, reported chiefly 

 in the third bulletin of the Illinois State Laboratory of Natural History, 

 showed that the principal food of all 3'oung fishes, with quite insignifi- 

 cant exceptions, consists of the very class of minute animal forms which 

 the bladderwort is constantly engaged in selecting from the water by 

 means of the hundred of bladders with which each plant is covered. It 

 thus not only occasionally entraps the youngest fishes, but likewise 

 habitually and continuously contends with them for food, and may be 

 said to thrive largely at their expense. 



Normal, III., August 29, 1884. 



