374 General Notes. [ May, 
arms, I have seen them push it from the rest of the body by 
alternately pressing against the sides with their hand-like front 
feet, in the same way that a person might strip off a tight garment. 
The skinning takes an hour or more, and after the integument is 
off they roll it up and swallow it. 
If kept in a warm room salamanders take food regularly dur- 
ing the winter and seem as lively as in summer. Tree toads kept 
in the same room will not eat. On the approach of cold weather 
they dig their way under sods and remain buried and torpid till 
spring. This would indicate that hybernation is not as settled 
a habit with these two species of salamanders as with the tree 
toads.— S. P. Monks. 
GROWTH AS A Function oF Cetts.—Dr. Charles Sedgwick 
Minot has published an article in the Proceedings of the Boston 
Society of Natural History on “ Growth as a Function of Cells.” 
This essay is an attempt to give an exact analysis of the problem 
of growth. The author considers that growth depends upon an 
impulse created at the time when the ovum is impregnated; this 
impulse he terms rejuvenation, because the vital power is made 
oung again in a new cycle of cells. The old cycle of cells 
passes away, the parent dies, but a new egg-cell is produced 
endowed with an extraordinary power of division, which causes 
the birth of successive generations of cells. Now usually the 
number of cells is doubled at every division, that being the least 
would be indefinite were there not an opposing influence. This 
opposing influence cannot be the loss of a part of the cells, as 
when part of the skin peels off, for this loss is too slight to coun- 
terbalance the multiplication. The explanation is, that the inter- 
vals between the births of two successive generations of cells — 
continually increases, or in other words the frequency of the 
divisions continually diminishes. This Dr. Minot calls the phe- 
nomenon of senescence, to which he attributes the utmost 
importance, as a vital phenomenon common to all animals, yet 
hitherto entirely unstudied. He says. “ From our point of view 
this change (in the frequency of division) is the most important 
alteration produced by senescence; that it really occurs is not 
only a deduction, but is shown by actual observation, for no one 
can question that the division of the cells during segmentation of 
the yolk proceeds at shorter intervals than during adult life; thus 
in an egg say eight or ten, perhaps more, generations of cells 
may be born in the course of a single day, all the cells dividing ; 
but we cannot for an instant imagine that all the cells of the 
human adult, for example, divide upon an average even once a day, 
probably * * * po T t x * epee coc ee 
But the size or weight of the whole animal depends not only 
