FINGER LAKES OF NEW YORK. 



235 



Table 16. — Division of Distribution of Summer Heat Income Between Sun and Wind in the 

 Lakes as a Whole and in Their Several Strata. (See figs. 3, 4, 5, and text.) 



(NoTK. — In this table, as elsewhere in this paper. " work " means the total work which would be needed to distribute the heat 

 from the surface of the lake through the adjacent water, computed on the assumption that all heat is put into place by the 

 wind mixing the warmer surface water with the cooler water below. In the division of the task of distributing heat between 

 sun and wind it is also assumed that all losses of heat fall on wind-placed heat. This evidently attributes too large a share 

 to the sun. Probably a fair estimate would be to allow to the sun all that it does below i m... i. e.. about loto ii per cent 

 of the total.] 



PLANKTON. 



The fresh-water organisms which constitute what is known as the plankton may be 

 separated into two groups, namely, (a) those forms which are large enough to be captured 

 readily vrith a regular plankton net whose straining surface is made of bolting cloth, 

 size No. 20 (new No. 25) and (6) those forms which are so small that they readily pass 

 through the meshes of this bolting cloth. The former constitutes the net plankton and 

 the latter may be called the nannoplankton. The latter term has been applied specifi- 

 cally to those organisms whose maximum diameter does not exceed 25 /i; but it is pro- 

 posed to extend the meaning of this term to include all of the material that passes through 

 the meshes of the net. The terms " macroplankton " and " microplankton " have been 

 used to designate these two groups. 



METHODS. 



The net plankton was obtained by means of a closing net which has been fully 

 described in a previous paper so that it is not necessary to consider it further here (Juday, 

 1916). The coefficient of this net is 1.2 ; that is, about 80 per cent of the column of water 

 through which it is drawn is strained. The catches from the diflferent strata were 

 concentrated in the plankton bucket ; the material was then transferred to 8-dram vials 

 and preserved in alcohol. In the enumeration the volume of the catch was reduced to 

 10 cm.^ after shaking thoroughly 2 cm.'' were removed with a piston pipette and the 

 Crustacea and rotifers contained therein were counted with a binocular microscope. 

 The number thus obtained multiplied by the factor five represents the total of such 

 organisms in the catch. When only a few of the larger Crustacea were present, the total 

 number was ascertained by direct count. The smaller organisms, such as the Protozoa 

 and algse, were enumerated by placing i cm.' of the material in a Sedgwick-Rafter cell 

 and ascertaining the number of the various forms in the usual manner by means of a 

 compound microscope. 



Samples of water for a study of the nanaoplankton were obtained by means of a 

 water bottle. The minute organisms were secured from these samples by means of an 

 electric centrifuge having a speed of 3,600 revolutions per minute when carrying two 



