Lake Maxinkuckee, Physical and Biological Survey 147 



occurred on the surface ranged in fine parallel lines, into which it 

 had been thrown by undulations of the water surface. 



Anabaena, after having been often seen, can easily be dis- 

 tinguished in the water by the naked eye, its peculiarities of color 

 and structure rendering it distinguishable from the other plankton- 

 algae. Both its appearance in mass and its microscopic appear- 

 ance differ somewhat under different conditions. Soon after 

 coming to the surface and forming a scum, especially after forming 

 a dense scum along shore, it changes in color from dark blue-green 

 to very pale blue, and the dense, tangled balls disintegrate into 

 single coiled filaments. In many cases great, thick masses were 

 formed along shore, especially in the bay southeast of the Academy 

 along the road, and then the algae apparently died. The water in 

 the vicinity became whey-like in appearance, and the mass had a 

 rank vegetable odor, so persistent that it remained after the addi- 

 tion of considerable formalin to vials containing the specimens. A 

 vial of the live material placed in the hot sun appeared to die soon ; 

 the water became decidedly milky and the cells became colorless. 



As the alga is known to disappear during the winter, close 

 watch was kept of the scum during the later part of the season to 

 observe what became of it. Late in the autumn it was found to 

 have sunken to the bottom along shore and was being covered up 

 by the forest leaves which fell into the water and sank to the 

 bottom. 



So far as observations go, it is not known whether this species 

 furnishes much food to the various animals of the lake or not. It 

 is a form which would be difficult to recognize in the stomach of 

 any animal, as the teguments are thin and the cells quickly sepa- 

 rate from each other, their attachment being weak. 



Because it forms a scum on the surface of the lake and along 

 shore, this plant is to some slight extent a nuisance. Its presence 

 in great profusion, as well as its unpleasant odor, detracts some- 

 what from the appearance of the lake. There is a prevalent no- 

 tion about the lake that the plankton-scum is poisonous, the effect 

 of it being to produce intense itching where it touches the skin. 

 No cases were observed, and no unpleasant sensations were ex- 

 perienced, however, and the few cases heard of which could be 

 reasonably authenticated might very likely be attributed to some 

 other cause, or to especial sensibility of the persons affected. 



Its exceptional abundance during the summer of 1906 was 

 followed by an exceptional abundance of entomostraca in the au- 

 tumn of the same year, and it is possible that there was some con- 

 nection between the two. 



