72 
tails from those occurring in fertilized eggs, but 
show a striking general parallel to them. The 
asters may be only two in number (cleavage 
asters), but as a rule there are many other asters 
(cytasters) that have no connection with the 
nucleus. Like the nuclear asters, however, 
the cytasters contain-centrosomes and may pro- 
gressively multiply by division. Cytasters and 
centrosomes are formed also in enucleated frag- 
ments obtained by shaking unfertilized eggs to 
pieces before treatment by the magnesium so- 
lution, and these asters may likewise multiply 
by division. 
These facts seem to leave no doubt of the 
formation of functional centrosomes de novo and 
independently of the nucleus. Evidence was 
adduced to show that the asters may operate 
as centers of cytoplasmic division, independ- 
ently of the necleus. It was also shown that 
the magnesium eggs show numerous gradations 
in the mitotic process between complete divi- 
sion and partial mitosis. 
FRANCIS E. Luoyp, 
Secretary. 
ACADEMY OF SCIENCE OF ST. LOUIS. 
AT the meeting of the Academy of Science 
of St. Louis of December 17, 1900, forty-six 
persons present, the following subjects were 
presented : 
Dr. O. Widmann read an account of the great 
St. Louis crow-roost, in which were embodied 
many facts concerning the life-history and 
habits of the common crow. 
Professor F. E. Nipher gave an account of 
some of his recent results in positive photog- 
raphy. He has now found that hydrochinone 
baths of normal strength may be used. The 
formula given in each box of Cramer plates 
yields good results, if the mixed bath is diluted 
with water to one-third strength. The potas- 
sium bromide may be left out, and one drop of 
concentrated hypo solution must be added for 
each ounce of diluted bath. The hypo has a 
most wonderful effect. With the same bath, 
plates may be developed as positives, in the dark 
room or in direct sunlight. He had even started 
the developing of a plate in a dark room, where 
it progressed very slowly, but satisfactorily ; 
continued the operation in diffused daylight in 
SCIENOE. 
(N.S. Vou. XIII. No. 315. 
an adjoining room, and finished the operation 
in direct sunlight. The process was accelerated 
by the light, but did not appear to be otherwise 
changed by the change in illumination. The 
resulting picture could not be distinguished from 
those produced by ordinary methods. This 
picture wasshown by means of the lantern. 
A box of Cramer’s ‘Crown,’ ‘Banner’ or 
‘Tsochromatic’ plates may have the plates indi- 
vidually wrapped in black paper, in the dark 
room or at night, and all the remaining work 
may be done in the light. A plate is taken 
from its wrapping into the lighted room and 
placed in the slide holder. After exposure it is 
taken out into the light and placed in the de- 
veloping bath, and the picture is then devel- 
oped in the light, and may be fixed in the light. 
Of course, during the changes the plate should 
be shielded from the light as much as is feasible, 
and the fixing bath may always be covered. 
But all the operations may be carried on 
without any dark-room conveniences that may 
not be secured even in the open fields. 
When weak hydrochinone baths are used, the 
picture, when developed in strong lamp-light, 
or in sunlight, has at first a golden-yellow color. 
When left in the lighted bath for an hour and 
a half, it slowly darkens to a nearly normal 
shade, as the details come out more sharply. If 
the exposure has been correctly made, there 
will be no trace of fog. With stronger baths, 
‘the picture comes out in the normal time, and 
has the normal shade. 
If the pictures are too dense, the remedy is 
to reduce the strength of the sodium carbonate 
solution, or to increase the amount of hypo in 
the bath. Very fine results are obtained with 
the sodium carbonate solution at half the 
strength given in Cramer’s formula. 
When the plate has been sufficiently exposed, 
a negative of the object can usually be seen 
upon the plate beforedevelopment. With long 
exposure this image is very distinct. It fades 
out in the bath, and the plate becomes clear. 
The shadows appear strongly but indistinctly 
at first, and of a pink color, and the high-lights 
stillappear white. The solution remains clear. 
Too much hypo will cause turbidity and a loss 
of detail. 
When the plate is exposed in a printing frame 
