Maxrce# 8, 1901.] 
In European starfishes multiple madre- 
poric plates occur in those forms that mul- 
tiply by self division. Hence they are the 
result of regeneration. This multiplicity 
is more frequent in starfishes, normally or 
abnormally, with more than five rays. The 
Cold Spring Harbor starfishes very freely 
cast off their arms when handled. Dothey 
practice autotomy in nature? 
Some Variations in Lucanus placidus, Statisti- 
cally Examined: HuizABeTaH B. MEEK. 
The mandibles of the stag beetles, espe- 
cially in the male sex, are extraordinarily 
developed and armed with teeth or pro- 
jections. These vary greatly in different 
species and in different individuals of the 
same species ; correlative with these differ- 
ences there are extreme differences in body 
length. In some species the variations are 
80 great that dimorphism exists, resulting 
in a division into high and low males. 
A quantitative expression for these differ- 
ences in size and form in Lucanus placi- 
dus, was sought, with the following results : 
The average body length is .4 mm. greater 
in the male than in the female and the 
coefficient of variation is greater; this is 
also true of the mandibles where the aver- 
age length is 2 mm. greater in male than 
female. The coefficient of correlation be- 
tween length of body and length of man- 
dible is .2 greater in the male than female. 
The teeth on the mandibles may be termed 
primary and secondary. A large or pri- 
mary tooth is invariably present on the 
mandibles of both male and female, but 
there is great variation in position, form 
and number of the secondary teeth even 
on the same pair of mandibles, as one cut- 
ting edge may have only one while the op- 
posite has any number of secondary teeth. 
Average number of teeth on mandible of 
male is 4 more than on female. There is a 
correlation between the number of teeth and 
length of mandible which is .2 mm. higher 
SCIENCE. 
375 
in males than females. Number of spines 
on fore tibizw varies from 6 to 11, with an 
average of 4 more upon tibie of males 
than females. 
It is thus found, as should be expecte d 
that variation is greater in the males than 
females. Also that there is no dimorphism 
in length of bodies, mandibles nor tibie. 
There is positive skewness in the body 
lengths and negative in the mandibles, but 
just what this may mean I am, at present, 
unprepared to say, as this study is prelimi- 
nary to a more complete one of the varia- 
tion and distribution of representative 
Lucanide in the United States. 
The Place-mode of Daphnia pulex, for Cold 
Spring Harbor, Long Island: H. M. Krwxy. 
The results of measurements of many 
organs on a large number of individuals. 
Contributions to the Biological Interpretation 
of Skew Variation: C. B. DAVENPORT. 
The paper presented conclusions based on 
a study of many cases of skew variation in 
organisms. 
The Genetic Development of the Forests of 
Northern Michigan: H. N. WuitForD. — 
This article will appear in full in an early 
issue of the Botanical Gazette. The factors 
controlling the distribution of plant soci- 
eties and formations are divided into three 
groups—climatical, ecological and histor- 
ical. These are discussed with special ref- 
erence to their effects on forests. 
A succession of plant societies on four 
sets of physiographic formations is recog- 
nized. In each instance the climax society 
is the deciduous forest. 
In the sand series the stages are beach, 
heath, coniferous forest and deciduous for- 
est. Here a controlling factor is the accu- 
mulation of humus. The pre-Cambrian 
rocks of the Marquette region offer an 
admirable field for the stages in the life- 
history of rock societies. Here not only 
humus, but inorganic soil, has to be accu- 
