Garman.] 
171 
[Jan. 16, 
its acquisition by the various species characterized by it. The work 
was based on material provided by the Museum of Comparative 
Zoology, at Cambridge, Mass., and the greater portion of the results 
was published in the Bulletin of the Museum, Vol. vm, No. 10, p. 
259. It was only by means of a stage from one species, a later 
from another, a still later from another, and so on, that the growth 
could be followed from the very early stages to the latest ; yet, the 
course of development being the same in all, it is evident that a se- 
ries formed thus would answer the purposes of the inquiry quite as 
well as if made up from any one of the species represented. In con- 
nection with the work, observations have been made on a large 
number of individuals, belonging to many species, venomous or non- 
venomous, in alcohol or living, captive or in the field. 
The snakes, without exception, so far as we know, have the habit 
of sloughing one or more times each year ; that is, they throw off 
the outer layer of the skin, the epiderm, from time to time. The 
number of times the slough is shed varies in different specimens, 
and, possibly, in the same specimen at different ages. A large “king 
snake” in my possession went through the process in April, July and 
December ; its mate did the same in March, May, August and Octo- 
ber. These snakes were kept in a warm room throughout the year, 
and the number of sloughs is probably more in each case than it 
would have been under normal circumstances, out of doors, where 
the animals had been allowed the customary winter sleep. Ordina- 
rily it appears as if not more than two sloughs are cast in a season : 
one on coming out of winter quarters in the spring, another about 
mid-summer or later. 
What appear like scales on the snake are really folds in the skin ; 
from these the slough comes off entire, extending over, around and 
under them, so that from head to tail it forms but a single piece of 
very thin horny material. As this is stripped off* it is generally 
turned inside out, excepting the little hollow cone covering the tip 
of the tail. This cone, or cap , as we shall call it, usually slips off 
without being turned ; its outlines are those of the extremity, behind 
the regularly arranged folds. On some of the serpents, kept under 
notice, the new epiderm was plainly visible, about three weeks be- 
fore casting the old. It was indicated by a milky appearance, just 
beneath the slough that was to be removed. As this whitish growth 
covered the whole body, eyeballs included, it interfered greatly with 
the vision. While ability to detect large shadows no doubt re- 
