416 



The absence of coarse vegetation, the sheltered situation 

 in a rift in a dense forest, and the shallowness of the whole 

 lake during much of the summer, permit an unusual range of 

 diurnal temperature-changes falling but a few degrees short of 

 the diurnal range in the air. The records (Table IX.) fre- 

 quently contain readings of 90° to 95° in the summer season. 

 This lake swarmed with the fry of various native fishes and the 

 introduced German carp, all of which make great inroads upon 

 the vernal plankton. It was also the favorite haunt of many 

 fish-loving water-fowl. This abundant animal life served in 

 turn to enrich the lake waters with its nitrogenous wastes, at 

 once available for utilization by the phytoplankton. There are 

 thus many chains of food relations in this lake, in most of 

 which, if not, indeed, in all, the plankton forms many links. 



COLLECTIONS. 



There is a total of 67 collections from this lake ; 1 only in 

 1894, 29 in 1896, 9 in 1897, 22 in 1898, and 6 in 1899. 



The single collection in 1894 was made by the oblique-haul 

 method. The absence of collections in 1895 is accounted for 

 by the fact that there was no water in the lake in that year. 

 In 1896-1899 collections were made in various w^ays according 

 to the conditions of access to the lake and the depth of the 

 water. Owing to rafts of driftwood, access at any season 

 through the slough is prevented. At high flood-levels, when 

 ice did not prevent, it w^as possible to enter the lake by boat 

 with our plankton pump and usual collecting apparatus. At 

 all other seasons access by boat was impossible, and apparatus 

 had to be carried across fields and through dense under- 

 brush to the lake, and collections made by wading out into the 

 lake or from a staging carried out from the shore for some dis- 

 tance over the w^ater. There are accordingly but 9 pump col- 

 lections. The remaining 57 were all made by dipping water 

 from the surface and pouring it through the plankton net. 

 Most of the collections represent, therefore, surface waters, but 

 owing to the exceedingly shoal water they are, nevertheless, in 



