ANNUAL DISTRIBUTION OF THE ORGANISMS. 21 



In general, the collections of the fall and -winter months were ^ 

 larger than those of the summer. 



The conditions of a deep lake seem to be more favorable to 

 the production of Notholca longispina than those of a shallow 

 one. Seligo states that it was found in greater numbers in the 

 deeper of the Stuhmer lakes. 



Notholca foliacea Ehrenberg. 



Notholca foliacea is not a common member of the plankton 

 of these lakes. T have found it in Green lake only once, on 

 May 4, 1901. In Lake Winnebago I found it in collections 

 made in the middle of February and in the middle of March, 

 1901. 



Asplanchna sp. ^.-U^y 



An undetermined species of Asplanchna was found in Green 

 lake in January and March, 1900. In the same winter it was 

 found in Lake Winnebago as early as November and was a 

 fairly constant member of the plankton until the middle of 

 March. 



Synchaeta pectinata Ehrenberg. 



Synchaeta pectinata occurred in Green lake in the winters 

 of 1900 and 1901. In the winter of 1900 it was found in the 

 months of February, March, and April. In 1901 it was found 

 from January to March. It was found in a single collection 

 also in October, 1900. In both winters the largest numbers 

 were in the collections made on the twenty-third of February. 



In Lake Winnebago it is also a winter form with a somewhat 

 more extended period of occurrence than in Green lake. I 

 have found it in the months from October to April, inclusive, 

 and in a single collection in June, 1901. 



This occurrence of Synchaeta pectinata corresponds fairly 

 well with (lie results obtained by European investigators. Ap- 

 stcin finds it a perennial form, with its maximum in the win- 

 ter months. He stales, however, that in his counting he has 

 not distinguished the species of Synchaeta, and it would seem 

 possible that pectinata did not occur in the summer months. 



