Garman.] 
175 
| Jan. 16, 
the cap, a fold, the anterior shoulder or chamber of the new cap, 
forms between the scaly skin and the anterior edge of the cap about 
to be set back as a ring. This part of the new cap does not grow 
within the old one, but under the epiderm in front of it. The slough 
of the button is connected with that farther forward until the latter 
is torn away. Externally the growing fold is so covered by the 
slough that it can not be seen ; in a section, fig. 6, it is shown in 
position, the old epiderm still covering it and connected with the 
old cap, the new ring. The operation of casting the old coat bears 
some resemblance to what occurs in crustaceans when the old shell 
is too small : the owner creeps out of it and at once forms a new 
one. There is this difference, however, the snake creeps only so 
far out of the cap as is made necessary by the new growth, and the 
swelling in the skin, at the time of the rapid production of dermal 
tissue. The increase in size itself pushes back the cap ; at the same 
time the first and second chambers of the latter are so closely filled 
by the tissues that it goes no farther back than it is crowded. The 
enlarged button is too bulky to be contained in the old cap, and the 
fold in front of the latter rises on the overplus. After the tumid 
condition is passed, the new cap shrinks a little more in proportion 
than the new ring ; this gives the freedom of movement needed for 
the rattling. The changes in the vertebrae of the button have gone 
on until a very substantial shaker has been formed, fig. 6. In- 
dications of the different vertebrae included are less distinct than in 
the preceding stages, but they are still apparent in the forward 
portion. The extent to which the transformation is carried is seen 
in fig. 8. In the specimen from which this sketch was taken the 
shaker is a very clumsy bone with scarcely any indication of the orig- 
inal constitution. It is surrounded by the thickened skin, except 
in front, where the muscles by which it is held and vibrated are 
attached. On its surface the shaker has a smooth and solid appear- 
ance, but if cut through longitudinally it is found to be lightly con- 
structed, to be full of cavities, and to contain the vessels of the 
column in their original positions, as before the consolidation. 
The large specimen from which figs. 7 and 8 were drawn has 
an entire series of eleven rings and a button. Each ring grasps 
two of the shoulders of that next succeeding it in time, and each, 
excepting the first, is grasped in the same manner by its predecessor. 
Not having been formed within a ring, the shape of the first, the 
hindmost of the series when present, differs from that of the others ; 
