1895.] Embryology. 499 
EMBRYOLOGY. 
Ascaris Eggs and Temperature.—Dr. Luigi Sala’ has applied 
the experimental method to the study of that classical object, the egg 
of Ascaris megalocephala. He exposed the eggs to a low temperature 
from 0° to 8° C. for an hour or more and then allowed them to de- 
velop under normal conditions of temperatnre, 25 to 30° C. 
In such eggs most noteworthy changes are found in the processes of 
maturation and fertilization. The changes that cold brings forth con- 
cern the penetration of the sperm, the structure of the protoplasm of 
the egg, the formation of the egg membrane, the arrangement of the 
chromatic substance and of the achromatic substance, the formation of 
the polar bodies, the formation of the pronuclei and of the first cleavage 
nucleus. 
These results of cold are illustrated by eighty-nine carefully executed 
figures and cannot readily be described in words, except in most gen- 
eral terms. 
The effect upon the egg that may be mentioned under the first cate- 
gory, the penetration of the sperm, are in some cases the prevention of 
any entrance, but in most cases the entrance of several or even as 
many as 12 sperms. 
That the protoplasm itself is changed is indicated by the fact that 
its staining reactions are different after the action of cold; while cer- 
tain changes in optical appearance are also brought about by the same 
agent. The membrane about the egg is quite noticably different in the 
cooled eggs; it may be formed but slowly and imperfectly and when 
formed be changed so remarkably as to fuse with the membranes of 
other eggs, at least so the author interprets certain monstrous com- 
pounds of several eggs enclosed in a common membrane. 
The spindels and their sharply marked groups of chromosomes ap- 
pear in the cooled eggs in quite different guises. The chromatic mate- 
rial may remain in long threads with irregular thickness instead of as- 
suming the characteristic two groups of four sharply circumscribed 
rods, The number of the chromatic elements is also changed in these 
abnormal eggs. The achromatic filaments of the spindles assume the 
most peculiar arrangements in double strands or sheafs, or in crossing 
1 Edited by E. A. Andrews, Baltimore, Md., to whom abstracts, reviews and 
preliminary notes may be sent. 
? Archiv. f. Mik. Anat., Feb. 1895. 
