137 



Stylaria lacustris (L.). Abundant. Taken in the plankton in 

 April. 



Nais elinguis O. F. Mull. Abundant. 



This species was identified in the plankton on April 29, 1895, 

 during the decline of the spring flood. 



Slavina appendiculata (D'Udekem) (Nais lurida Timm.). Fre- 

 quent. 



Ophidonais serpentina (O. F. Mull.) (Nais serpentdna O. F. Mull.). 

 Frequent. 



Dero limosa Leidy. Abundant. 



Dero obtusa D'Udekem. Abundant. 



This species was taken in the plankton in July and August, 1895, 

 during the run-off of impounded waters from recently invaded back- 

 waters. (See Pt. I., PI. IX.) 



Dero vaga (Leidy). Abundant. 



Two individuals (Part I., p. 297) were found in channel waters in 

 stagnation conditions under the ice on February 23, 1895, at a time 

 when the plankton was almost entirely exterminated. Under 

 normal conditions we have no evidence that this species is more 

 abundant in stagnant waters. 



Dero furcata Oken. Frequent. 



Pristina leidyi Smith. Abundant. 



Pristina flagellum Leidy. One specimen. 



Ch&togaster limncsi v. Baer. Abundant. 



Ch&togaster diaphanus Gruith. Abundant. 



ChcEtogaster diastrophus Gruith. This is apparently the most 

 abundant species of the order in the plankton, having been identi- 

 fied in all months but January and May, especially at times when 

 impounded flood waters are drained off from backwaters, as, for 

 example, in the March flood of 1895. 



jEOLOSOMATIDjE. 



ALolosoma hemprichii Ehrbg. Frequent. 

 ALolosoma tenebrarum Vejdovsky. Abundant. 

 ALolosoma sp. Abundant. 



For reasons assigned above, the great majority of the oligochastes 

 in the plankton remain unidentified and are included in our records 



