No. 388.] REVIEWS OF RECENT LITERATURE. 339 
the surface contained few Entomostraca, but these increased at this 
level during the night, the Copepoda appearing before the Cladocera, 
the maximum being attained at 4 a.m. The night catches at the 
surface and at 20 meters contained great numbers of Ceratium in 
division. Migration, reproduction, and growth are all factors in this 
increase in the nocturnal plankton in the superficial layers. No 
report is made upon the total vertical content of the water, and the 
data do not afford any clue to the extent of the migration suggested. 
The position of the thermocline is not indicated. aur Oe a 
Plankton of the Oder.!— This potamoplankton is characterized 
by Schroder as variable, being at a minimum during the winter when 
the stream is frozen, and in March when it is at flood and full of silt. 
It attains a maximum during a period of low water in the latter part 
of the summer. The plankton of the main current is less abundant 
than that of contiguous bays or of adjacent ponds supplied by the 
river. It is suggested that the plankton content of flowing water is 
inversely proportional to the fall of the stream. At all times the phy- 
toplankton of the Oder is relatively small, and is largely composed 
of diatoms. In the shallower and warmer water of the ponds the 
Bacillariacee are replaced by the Chlorophycee and Phytomasti- 
gophora. Thus, in general, the diatoms thrive best in cooler water, as 
in mountain lakes and cold streams, while shade and access of run- 
ning water favor their development in ponds. In the plankton of 
_ the Atlantic Ocean, also, the diatoms predominate in the arctic waters, 
and are replaced by the Peridinidz:and Schizophycee in warmer 
regions. CAK 
Notes on Nematode Parasites.— 1. It is not often that one is 
called upon to record valuable contributions to zoological literature 
from the pen of a botanist, but the recently published work of Stone 
and Smith ? on nematodes is deserving of more than passing notice. 
The root-galls produced by certain species of this group are the cause 
of considerable damage among cultivated plants, and the authors, 
‘who were drawn to investigate the subject by reason of its economic 
importance and bearing on their own department, have given it 
1 Schröder, B. Planktologische Mitteilungen, Biol. Centrald., Bd. xviii (1898), 
pp. 525-535: 
2 Stone, Geo. E.,and Smith, Ralph E. Nematode Worms, Division of Botany, 
Bull. No. 55, Hatch Experiment Station Mass. Agr. College (November, 1898). 
67 pp., 12 plates. 
