159 



An examination of the location of the pulses of Asplanchna 

 brightwellii shows (Table I.) that in 1898 one coincided with the 

 pulse of chlorophyll-bearing organisms (PI. II.) and the remaining 

 four followed it either in a week or fortnight. In previous years 

 two pulses coincide with and five follow those of chlorophyll-bearing 

 organisms, and a single ill-defined one (Nov. 14, 1895) precedes. 



This species is not wholly herbivorous in its feeding habits. 

 Codonella, Difflugia, and even other rotifers such as Brachionus and 

 Anur<za,&re frequently seen in the digestive tract. _Diatoms, even 

 Melosira and Peridiniidce, as well as Pediastrum and other algas, are 

 frequently taken as food. In one instance a Daphnia cucullata 300 /* 

 in length was seen in the stomach in a transverse position. It was 

 fully a third the length of the animal which had eaten it. 



Asplanchna brightwellii is reported by Skorikow ('97) in the 

 summer plankton of the Udy, in Russia ; by Schorler ('00) as spo- 

 radic in the Elbe in June and September; and by Lauterborn ('93) 

 from the Rhine, where its cycle coincides with that of A. priodonta. 

 Zacharias ('98) reports it in German reservoirs in June and August. 

 It is a cosmopolitan species, but does not seem to have been found 

 by other plankton investigators in European waters. 



Asplanchna ebbesbornii Huds. Average number of adults in 

 1895, 942. In 1898, only winter eggs of the species were noted in 

 the plankton in February, June, July, September, and October, 

 though adults were doubtless there. Adults have doubtless oc- 

 curred sporadically in all other years, and in 1895 reach a pulse of 

 21,518 on July 6 at 81, which was followed by the appearance of 

 males and winter eggs. All records of adults lie between April 29 

 and September 14 and above 60. This rare rotifer has not appeared 

 in the literature of fresh-water plankton elsewhere to my knowledge. 

 Hempel's statement ('99) that his record of its occurrence in the 

 Illinois is the first for this continent must be modified, since Leidy 

 ('87) found it near Philadelphia. It is evidently a summer plank- 

 tont in our waters, and the wide distribution of its winter eggs 

 suggests that it, too, may be poly cyclic ; and their appearance 

 in the plankton in large numbers with reference to the adults taken, 

 leads to the further inference that its center of distribution is prob- 

 ably not in channel waters, and that it may be predominantly 

 limicolous species, or have its center of distribution in the quieter 

 backwaters. 



