175 



channel waters. Schorler ('00) reports the species as sporadic in 

 the Elbe, and Skorikow ('97) finds both B. bakeri and its variety 

 brevispinus sparingly in the Udy in summer months. 



This species in common with other Brachionida: was infested by 

 Bimcerium hyalinum Przesm., and occasionally by a filamentous 

 fungus-like growth. Empty loricae were wont to appear with the 

 culmination of a pulse and subsequently. No males were identified 

 as belonging to this species, and attached male eggs were recorded 

 only late in September, 1897, at the close of an unusual pulse. They 

 were found on var. cluniorbicularis and rhenanus. Females with 

 winter eggs were not at any time recorded for this species. It may 

 be that some of the free winter eggs referred to the genus Brachionus 

 (Table I.) belong to this species. The recurrent pulses are similar to 

 those of known poly cyclic species, and we may infer the probability 

 of such a phenomenon in B. bakeri, though conclusive proof of its 

 occurrence is not found in the statistical records. 



Brachionus budapestinensis v. Daday. Average number of 

 females, 4,211; of eggs (carried), 740. This is one of the most 

 sharply defined species of Brachionus and a typical planktont of 

 open waters. It has, moreover, a sharply limited seasonal distribu- 

 tion in which it is apparently poly cyclic. The appended table gives 

 the dates and temperatures of appearance and disappearance and 

 the pulses in the several years. 



In the main, the period of occurrence is practically from the end 

 of June till the early part of October and above 60. A record in 

 May, 1896, and an isolated one in December of the same year, indicate 

 an extension of this period, but such occurrences are rare and 

 irregular and the numbers small. This abrupt decline in 1898 as 

 temperatures pass 60 (PI. XII., Pt. I., and Table I.) is paralleled 

 in previous years. The normal seasonal routine seems to be as 

 follows: The species reappears in the plankton in May- June at 

 70, rising slowly to its first pulse (average, 26,104) in July, with a 

 larger pulse (average, 184,453) in the following month during the 

 maximum heat, and a much smaller one (average, 10,044) in Sep- 

 tember, followed immediately by an abrupt decline. The average 

 temperature of the larger pulses lies close to the season's maximum, 

 while the latest pulse, at the lower temperature (72.2) averages but 

 10,044. These data all indicate that this is a midsummer planktont, 

 with its optimum temperature near the summer's maximum. The 



