155 



PULSES OF ANUR/EA HYPELASMA. 



August pulse 15,200 eggs were found on the rise to 4,000 on the 

 decline. 



The location of the pulses of A. hypelasma is of special interest. 

 It will be seen in Table I. that they occur in 1898 in the same col- 

 lections in which the pulses of the other species of Anuraa and many 

 other rotifers occur, or in collections but a week removed. They 

 coincide in general with dates of the ploiman maxima noted in the 

 opening discussion, and exhibit the same correlation with hydro- 

 graphic conditions and intercalation with the pulses of chlorophyll- 

 bearing organisms which were noted in the general discussion and 

 have been found in preceding species. The comparison with Anur&a 

 of the cochlearis group affords a curious instance of an entire sup- 

 pression (Table I.) of one species of a genus (cochlearis} in the month 

 of August and the occurrence of a normal pulse in another (hypelas- 

 ma}. Comparison of the distribution of cochlearis in previous 

 summers would lead us to expect a cochlearis pulse in August, 1898, 



