NAIDIDA. 
Stylaria lacustris (L.).—Abundant. Taken in the plankton in 
April. 
Nats elingumts 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) (Nats lurida Timm.).—Fre- 
quent. 
Ophidonais serpentina (O. F. Mull.) (Nats serpentina 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- 
maners. (cee Pt. I., Pl. TX.) 
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, ata time 
when the plankton was almost entirely exterminated. Under 
normal conditions we have no evidence that this species 1s more 
abundant in stagnant waters. 
Dero furcata Oken.—Frequent. 
Pristina leidyt Smith.—Abundant. 
Pristina flagellum Leidy.—One specimen. 
Chetogaster limnei v. Baer.—Abundant. 
Chetogaster diaphanus Gruith.—Abundant. 
Chetogaster 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. 

AZOLOSOMATID. 
Atolosoma hemprichi Ehrbg.—Frequent. 
A‘olosoma tenebrarum Vejdovsky.—Abundant. 
A£olosoma sp.—Abundant. 
For reasons assigned above, the great majority of the oligochetes 
in the plankton remain unidentified and are included in our records 
