282 THE AMERICAN NATURALIST. (VOL: XXXII; 
eggs any trace whatever of centrosome or archoplasm in connection 
with either nucleus. In more favorable sections at this stage, how- 
ever, an archoplasmic field, very faint at first, but later showing 
centrosomes and radiations, is observed by Wheeler lying close to 
the egg nucleus, but no indication of such structures is found near 
the sperm nucleus. Kostanecki’s observations, on the other hand, 
are precisely the reverse, the centrosome and archoplasm, when 
visible at all, being seen just outside the membrane of the sperm 
nucleus, while nothing of the kind accompanies the egg nucleus. 
Here we are confronted by totally contradictory observations of 
two able investigators, working on the eggs of the same species of 
animal, and until one or the other author is confirmed by future 
study of the fertilization of the egg of Myzostoma glabrum judgment 
in this case will have to be withheld. 
The doubt which Wheeler’s work, of late the sole remaining con- 
tradiction, has seemed to cast on the universal validity of Boveri’s 
view throughout the animal kingdom is, at all events, greatly dimin- 
ished by the recent publication of Kostanecki. 
GEORGE LEFEVRE. 
Plankton Studies on Lake Mendota.'—This paper, being a report 
of the continuation of Professor Birge’s work on Lake Mendota, is 
by far the most important American contribution, to our knowledge, 
of the biology of lakes. It contains the results of observations and 
collections made at maximum intervals of two weeks during a period 
of two years and a half. These observations have been worked out 
with infinite care and patience, and the conclusions are of very great 
interest. The author does not maintain that the conclusions are in 
all cases final, as, indeed, that would be impossible, because of the 
very complex character of the problems attacked. But he certainly 
is to be congratulated on the amount he has been able to accomplish. 
It is impossible for a reviewer, within any reasonable limits, to 
treat of the paper, for, while it is a somewhat bulky production — 
covering 174 pages of the eleventh volume of the Zransactions of the 
Wisconsin Academy — it is really.so much condensed that one cannot 
make an abstract of its contents. All that’can be attempted is to 
indicate the subjects treated. 
After a brief discussion of the methods employed in the investiga- 
tion, the divisions of the paper are taken up in the following order: 
1 Plankton Studies on Lake Mendota. II. The crustacea of the plankton, 
pe aed ene = By E. A. Birge, vee of Zoology in the University 
f Wisco . Wisconsin Acad. Sci., 
