624 
distinguished by sexituberculate superior mo- 
lars. 
Dr. Hay called attention to the fact that for 
a long time there has been much discussion re- 
garding the origin of the elements entering into 
the shell of turtles. As to the bones known as 
costal plates, the great majority of anatomists 
have held that they have resulted from the 
union of dermal bones with underlying ribs: the 
neural plates from the union of dermal bones 
with the neural arches. Recently Goette has 
studied the development of the costals and 
neurals in the young of Chelone squamata. He 
finds that the whole costal plate develops con- 
tinuously from bone which appears beneath 
the perichondrium of the cartilaginous ribs. 
No part of either the costal or neural plates : 
arises in the skin. While accepting Goette’s 
results as established, the speaker did not ac- 
cept his conclusion. Neither did he accept the 
other view that the costals and neurals are 
composed of dermal bones united with those of 
the internal skeleton. The speaker held that 
there were originally three strata of bones on 
the dorsal surface of turtles. One of these was 
in the skin, and is represented by the mosaic 
found in the skin of Dermochelys. Another 
layer was sub-dermal, and this united with ele- 
ments of the third stratum, namely the ribs and 
neural arches. This union has become so com- 
plete that the bones arise from the same 
centers. These three strata of bones on the 
dorsal surface correspond to those which are 
found in the ventral wall of the caiman, viz: 
true ribs, ‘abdominal ribs,’ and bony dermal 
scutes. 
Mr. Bigelow compared the germ-layers of 
various Crustacea with special reference to the 
Cirriped Lepas. It was pointed out that in the 
cleavage leading to the segregation of the germ- 
layers there are very many resemblances be- 
tween Lepas and other Entomostraca. Lepas 
resembles most other Crustacea in respect to 
the position of the blastopore, and the exten- 
sion of the entoblast and mesoblast from that 
region as a starting point. In Lepas also the 
mesoblast and entoblast originate from cells 
which, speaking in general terms, lie at first in 
the blastoderm and later migrate into the 
cleavage cavity. But among these immigra- 
- SCIENCE. 
[N.S. Von. XIII. No. 329. 
ting mesentoblastic cells one can distinguish the 
individual cells of entoblast and two varieties 
of mesoblast, entomesoblast and ectomesoblast. 
There are observations indicating that similar 
conditions exist in other Crustacea. 
Henry EH. CRAMPTON, 
Secretary. 
SECTION OF ASTRONOMY, PHYSICS AND CHEM- 
ISTRY OF THE NEW YORK ACADEMY 
OF SCIENCES. 
A REGULAR meeting of the section was held 
on April 1, 1901. The first paper was by Mr. 
H. C. Parker, on some ‘Experiments on 
Standards of High Electrical Resistances.’ 
The author briefly described the usual methods 
employed in the measurement of high re- 
sistances and then gave an outline of Professor 
Rood’s electrometer method (American Jour- 
nal of Sciences, Vol. X., October, 1900, pp. 285— 
294). By this method it seems possible to 
measure resistances as great as 1,000,000,000 
megohms, while by the direct deflection 
method the practical limit was stated to be 
about 100,000 megohms. 
The author gave the results of a series of 
measurements made on a new form of standard 
high resistance, devised by Professor Rood. 
This form of standard consists of oxide of man- 
ganese on cobalt glass. It gives a convenient 
means for obtaining resistances of from one to 
ten thousand megohms. Most of the measure- 
ments were for the purpose of determining the 
best protective insulating material with which 
to coat the above resistances. The author 
stated that the work was still in progress. 
Professor J. K. Rees then presented a paper 
on ‘Temporary Stars, with Especial Reference 
to the New Star in Perseus.’ Professor Rees 
explained the present classification of variable 
stars and gave illustrations of each of the six 
classes. A history of the discovery of the new 
star in Perseus was given and photographs of 
its spectrum were exhibited. Brief mention was 
made of the various collision theories proposed 
to account for the evidence of two light sources 
which appear involved. The light curve of 
the new star was referred to, showing how 
rapidly the star increased to the 0 magnitude, 
