190 General Notes. 
on one side. If it is placed upward, the respiration of the embryo 
is hindered. The embryoscope can be turned up at any moment, 
and kept upright for five minutes at a time without injury to the 
mbryo. 
With 2 little practice, the whole process of arming an egg with 
the embryoscope may be completed in from six to eight minutes. 
The embryoscope is well adapted for purposes of class-demon- 
stration, for investigating the growth of the various parts of the 
embryo, and the physiological processes during embryonic life, as 
the action of the heart, movements of the body, etc. It is indis- 
pensable to him who would study the effects of external agents 
upon the embryos of warm-blooded animals; and must be of great 
service where it is required to determine the precise stage of devel- 
opment before removing the embryo from the egg. It has been 
found useful in studying the formation of double embryos. Fene- 
strated eggs have been successfully incubated up to the thirteenth 
day, and it is probable that under favorable conditions the embryos 
of such eggs would reach maturity. 
On the fifth day, it is still easy to bring the embryos under the 
window. On the sixth and seventh days, it is more difficult. At 
this period the change in the position of the embryo, which requires 
from five to ten minutes, should take place in the incubator, 
After the eighth day, the embryo cannot be brought under the 
window. If it be necessary to determine whether such an egg or an 
older one still lives, we have only to leave the egg for several hours 
in the incubator with the window directed upwards a little, after 
which, by strong reflected light, one may readily see the blood 
circulating through the channels of the vascular area. 
PROCEEDINGS OF SCIENTIFIC SOCIETIES. 
ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA.—Sept. 
20, 1887.—Mr. G. H. Parker gave an historical sketch of investi- 
gations upon the eyes of arthropods. Grenacher’s theory of the 
hypodermal origin of the retina, developed by involution, has been 
borne out by later studies, From a study of the nerve distribu- 
tion, the speaker believed the three-layered eye to be evolved from 
that with one layer. | 
r. Meehan stated that in Mesembryanthemum and similar 
plants, the glands of which develop in inverse proportion to the 
roots, chemical analysis sometimes determines the presence of more 
nitrogen than can be obtained from the soil. It was suggested that 
the glands absorbed the gas from the atmosphere. 
Mr. H. T. Cresson exhibited specimens of prehistoric implements 
collected from beds surrounding what had probably been pile dwell- 
ings on the mud flats of the Delaware, near Naaman’s Creek. 
