166 



near the summer maximum. The location of the pulses with respect 

 to those of the chlorophyll-bearing organisms (PL II.) shows in the 

 main the same relation that has been observed in other ploiman 

 rotifers. In 1895, three angularis pulses lie in the period common 

 to both, one of these coinciding in location and two following at the 

 next collection. In 1896, two coincide and five follow at the next 

 collection or shortly thereafter. In 1897, four follow at an interval 

 of a week or a fortnight, and one is located where data are incom- 

 plete. In 1898, three coincide and three follow at a short interval, 

 and one (June 7), a minor and ill-defined pulse, appears to lie on the 

 rise of the pulse of the chlorophyll-bearing organisms. In the main 

 the dependence of these rotifer pulses upon the recurrent periods of 

 increase in these primal links in the food cycle is suggested by this 

 coincidence or sequence. The pulses of Brachiomis angularis co- 

 incide in the main with those of the totals of ploiman rotifers 

 (Table I.). 



There is no vernal pulse in the species at the time of the April- 

 May volumetric maximum, and no large autumnal pulse. The pulses 

 in August-September, at the close of our period of maximum heat, 

 average much greater than those of other months, and still further 

 indicate the relation of this species to the higher temperatures. 



The eggs are carried by the female attached to the posterior end 

 of the lorica. Usually but a single summer egg is carried at one 

 time, but often two, three, and even four, have been seen during the 

 height of the period of rapid reproduction. The relation of the 

 number of eggs to the pulses is obscured in this species to some 

 extent by the fact that the eggs are similar to those of other Brachio- 

 nus and when detached cannot be identified with certainty. Records 

 are therefore based upon attached eggs only. The number of these 

 depends to some extent on the detachment in the processes of 

 collection, killing, and subsequent handling. In a few cases de- 

 tached male or winter eggs could be identified with some degree of 

 probability by the constitution of the rotiferan plankton. An 

 examination of the records of eggs (Table I.) will, however, suffice to 

 indicate the prevalence of rapid reproduction during the rise of the 

 pulses and the decline in the process during the fall of the pulse. 

 Males, male eggs, and winter eggs were recorded in a number of 

 instances at the culmination or during the decline of a pulse. For 

 example, in 1898, they followed the pulses of August 16, September 



