216 



Eggs of this species are not carried by the parent for any length 

 of time, so that reproductive cycles are not easily traced. The total 

 number of the summer eggs of Synchceta will be found (Table I.) to 

 fluctuate somewhat with the pulses of the species. The free winter 

 eggs, belonging probably to both species of Synchatta, also show 

 some tendency to predominate at and after the culmination (Table 

 I.) of the pulses. A female carrying a male egg w T as recorded during 

 the rise of the spring pulse in 1898, and attached winter eggs were 

 noted at the vernal pulse in 1895 and 1897. The evidence points 

 toward the culmination of these pulses in a sexual cycle. 



The soft and flexible nature of this rotifer and the absence of 

 spinous outgrowths have made whatever variability the species 

 possesses less evident than it is in such a genus as Brachionus. There 

 is considerable variation in size possibly due to age even in the 

 same collection. The determination of preserved material of this 

 genus is fraught with insuperable difficulty. The separation of 

 pectinata and stylata in our records is at the best only probable. It 

 may be that other species of Synchceta have been included w r ith the 

 individuals referred to stylata. In any event the result of the 

 division has led to symmetrical results comparable with those of 

 other planktonts. Synch&ta is often parasitized at the times of the 

 larger pulses by some sporozoan (?). At the maximum of the 

 vernal pulse in 1898 over 4 per cent, of the individuals were thus 

 affected, the infestation continuing through the decline of the pulse. 

 External parasites, Colacium and Rhabdostyla, are rare. 



This species has not been found widely in the plankton, possibly 

 because of the confusion of stylata, tremula, and pectinata in identifi- 

 cation. From the large numbers reported in almost every instance 

 where it has been found, the expectation of its wide-spread occur- 

 rence is at least raised, waiving in this connection the possibility of 

 specific confusion. Jennings ( '94) found it to be very abundant in 

 towings in Lake St. Clair, and ( '96) in Lake Michigan near Charle- 

 voix. He finds it less abundant in the summer plankton of Lake 

 Erie ('00). Stenroos ('98) reports it as one of the most abundant 

 limnetic rotifers in Lake Nurmijarvi in Finland in the summer, and 

 Skorikow ( '97) finds that next to Polyarthra it is the most abundant 

 rotifer in summer months in the River Udy near Charkow, Russia. 

 His figures of occurrence show some traces of recurrent cycles in 

 these months, with maximum numbers at the first of August. Lau- 



