JANUARY 11, 1901.] 
under either a negative or a positive, an expo- 
posure of half a minute to diffuse daylight is 
ample, with an ordinary jnegative. The plate 
may be over-exposed by placing it for a long 
time in direct sunlight, and it will then appear 
on development somewhat like an over exposed 
negative. This has not yet been tried with hypo 
in the bath. 
Professor Nipher showed a preliminary dia- 
gram in which exposure and illumination of the 
developing bath were taken as} coordinates. 
The zero condition was represented by a line, 
and the conditions for producing direct and in- 
verted pictures were represented by areas. 
He also exposed and developed, in a common 
bath, in the lighted audience room, negatives 
printed from negatives and positives printed 
from positives. 
The possible value of radio-active substances 
acting upon the developing plate in place of or 
in addition to light was referred to as a most 
promising field for study. 
Professor Nipher stated that he had done no 
work with the plates of other makers, since he 
found on trial that one such plate did not give 
good results with the treatment that had suc- 
ceeded with the Cramer plates. 
One person was elected to active membership. 
WILLIAM TRELEASE, 
Recording Secretary. 
ZOOLOGICAL CLUB, UNIVERSITY OF CHICAGO. 
Tue first meeting of the Quarter, October 
17th, was devoted to a paper by Miss Mary 
Hefferan, giving the results of her researches 
on the variation of the teeth in the jaws of 
Nereis. This paper will appear elsewhere in 
full. 
At the second session of the club, October 
31st, Mr. R. 8. Lillie gave an account of some 
experimental work upon the reactions of Areni- 
cola-larvee which was carried on by him during 
the lastsummer at Woods Holl. The following 
is a brief abstract of Mr. Lillie’s paper : 
In the swarming stage (in which three 
setigerous trunk segments are present) the 
larve are positively heliotropic and negatively 
geotropic, and in consequence collect at the 
surface of the water on the light side of the 
dish. After the fourth segment has appeared 
SCIENCE. 
73 
the cilia are lost, the larv settle to the bottom, 
and the heliotropism becomes negative. The 
heliotropic response is due to the rays at the 
blue end of the spectrum, the red rays being 
apparently inactive. 
The normal reactions of the swarming 
larvee are altered under the following arti- 
fically induced conditions: (a) rise of temper- 
ature of the sea-water, (5) dilution or concen- 
tration of the sea-water within certain limits, 
(c) alteration of the chemical constitution of the 
medium. Rise of temperature above 85° is 
followed by loss of heliotropism and a gradual 
settling of the larvee to the bottom ; on cooling, 
however, heliotropism and negative geotropism 
largely appear. In dilute or concentrated sea- 
water the heliotropism in a large proportion of 
larve is altered from positive to negative ; the 
same happens in slightly acidulated sea-water 
(though the effect here soon passes off and 
positive heliotropism reappears) and also in 
artificial solutions containing NaCl, CaCl,, and 
MgCl, in certain proportions. 
Solutions of different salts affect ciliary and 
muscular movements in definite and character- 
istic ways. A fact of particular significance is 
that in the same solution one form of motility 
may be affected very differently from the other. 
Pure 5/8n NaCl solutions immediately arrest 
ciliary movement and cause a liquefaction and 
dissolution of the cilia; towards muscular 
movement its action is decidedly less injurious. 
The poisonous effect of the pure solution is, 
however, diminished by dilution, and also by 
the addition of small quantities of other salts, 
especially CaCl, and MgCl,. Solutions con- 
taining two salts in favorable proportions pre- 
serve ciliary and muscular activities for con- 
siderable periods, each form of activity having 
its own characteristic optimum solution which 
differs from that of the other. Pure CaCl, solu- 
tions and pure MgCl, solutions, and their mix- 
tures, quickly arrest muscular activity and 
cause the larvee to become perfectly rigid within 
a few minutes; while ciliary movement may 
continue in these solutions in some cases for 
hours after muscular movement has ceased. 
The larvee, although capable of swimming about 
actively in these solutions, quickly lose all 
power of heliotropic orientation as their power 
