295 



Eighty-four per cent, of the 38 hauls do not vary more tlian 20 per cent and 

 only one over 25 per cent. This variation is slightly greater than in the results 

 obtained by Apstein and Reighard. 



Station IV was selected for the purpose of studying changes in distribution 

 from day to day by making daily hauls, but this plan was not carried out. How- 

 ever, five hauls were made here in July and eight in August at a depth of six 

 meters. Those made in July have an average of 12.26 cc. of plankton per cu. m. 

 of water, while the eight made in August have an average of Hi. 86 cc. per cu. 

 m. of water. This increase of 4.6 cc. is due to the natural seasonal variation, as 

 Apstein (1892) found that there is a rapid increase in the quantity of plankton 

 during August and September, reaching a maximum about the 1st of October. 



Turkey Lake is comparatively rich in plankton. Dobersdorf See, which is 

 classed as "plankton rich" by Apstein, contained in July, 1892, 1,062 cc. of 

 plankton under one sq. m. of surface at a depth of 20 m., or -).3 cc. per cu. m. of 

 water. One haul (III) in Turkey Lake, July 2, shows that it contained 348.6 

 (69.73x5) cc. under one sq. m. of surface at a depth of nearly 20 m., or 18.15 cc. 

 per cu. m. of water. Thus Dobersdorf See contained not quite three times as 

 much plankton. In comparison with other North American lakes, Turkey Lake 

 has from thirty to fifty times as much plankton in August as Reighard (1893) 

 found in Lake St. Clair in September, and from fifteen to twenty times as much 

 as Ward (1894) found in Lakes Michigan, Round and Pine at the same depths 

 and during the same month, August. 



A surface stratum about three meters deep contains most of the plankton of 

 Turkey Lake. The average number of cc. per cu. m. of water for the ten hauls 

 made at a depth of three meters is 36.4, for thirty-one hauls made at a depth of six 

 meters it is 14.8. By means of a pump, a piece of rubber hose, and a small net 

 of No, 20 bolting cloth, it was found that very few organisms live below a depth 

 of six meters and scarcely any but Oligochetes below fifteen meters. Three hauls 

 (Illfi, IVj, XXg) present some difficulties which are still unexplained. They are 

 hauls from a depth greater than six meters, and show a smaller quantity of plank- 

 ton actually taken than hauls made just before or immediately after at a depth of 

 six meters. This difficulty was not noticed, however, in time to make further 

 hauls in the same manner to see if an explanation might be found. The unusu- 

 ally large quantity taken id hauls XIV and XV is probably due to a local accumu- 

 lation, as the wind on the previous day was of such strength and from the proper 

 direction to cause such. 



To sum up — 



1. The plankton of Turkey Lake is quite uniformly distributed. 



