177 



relation of hydrographic conditions to the relative development of 

 pulses in different years is seen on a comparison of the record for 

 1896 and 1897, the former (Pt. I., PI. X.) being a year of recurrent 

 floods and the latter (Pt. I., PI. XI.) one of stable conditions 

 through the greater part of the seasonal distribution of the species 

 in question. The average numbers in these two years were 3,105 

 and 31,306, respectively, and the average amplitude of the pulses 

 18,250 and 97,200, showing, respectively, a ten- or five-fold increase 

 in the latter year. The extension of the heated termjnto September 

 in 1897, is reflected in the large September pulse (552,000) and in 

 the extension of the period of occurrence into October. 



The locations of the pulses of Brachionus budapestinensis in 1898 

 correspond with those of the Ploima in general. They likewise 

 coincide with or follow those of the chlorophyll-bearing organisms 

 (cf. PI. I. and II. with III. and IV. and Table I.). Similar relations 

 are apparent in 1896 and 1897 but are less evident in prior years. 

 They suggest an interrelationship of the pulses in this species with 

 the fluctuations in the food supply. 



Males, male eggs, and winter eggs were not recorded, but the 

 recurrent pulses in this species are so similar to those in other rotifers 

 in which the evidence of the occurrence of sexual reproduction at 

 the culmination of each pulse has been found, that the inference 

 may be made that this species likewise is poly cyclic in our waters. 

 Females carrying one or two summer eggs have been found in 

 greatest abundance during the rise of the pulse, and only in small 

 numbers, if at all, during its decline. 



This species is subject to some variation in the development of 

 surface ornamentation, in the ratio of width and length, and in the 

 curvature of the median spines. It is usually somewhat more 

 slender than figured originally by v. Daday ('85) or even by Hempel 

 ('96) , who described a form somewhat more slender than that figured 

 by v. Daday, as B. punctatus. Shortly afterwards Skorikow ('96) 

 described the same species as B. lineatus from Russian waters. The 

 name given by v. Daday has, priority, and as neither the Russian nor 

 the American forms are to my mind well enough set off to merit 

 even varietal distinction, I have used the name given by v. Daday, 

 and have included under it both wide and narrow forms and those 

 with incurved or outcurved median spines. The fact that their 

 common record of seasonal distribution forms a seasonal curve of 



