62 
ANIMAL LIFE ON THE 
how much more so are those delicate things ; but this again 
has not been overlooked, for a careful scrutiny with the 
glass reveals the facts that they are actually incased within 
the tube of the pedicellariae. Thus, we see, in addition to 
its other work, the pedicellariae acts as the protector of the 
young spine, but it is at the expense of its own existence ; 
for when the spine arrives at a size too large for the tube, 
its rapid revolutions put a cork-screw twist upon the inner 
lining, thereby choking up the passage, then the whole tube 
speedily dissolves and leaves the young spine free. 
When within the tube, the casual observer is apt to be 
deceived by the appearance and size of these tender things, 
and suppose them to be something else ; but extract them 
from the tube, and place them under a powerful microscope, 
and the identity is indisputable. 
When immediately extracted from the skin, owing to 
the soft condition of particularly the upper portion of the 
stalk, it is very liable to break away ; but when left for a 
few minutes to the exposure of the air, it hardens into the 
white limy condition of the adult spine. Examining their 
construction carefully, the characteristics of the spine are 
easily traced in the interior rings and fluted columns, and at 
the base the socket is always found in a perfect state. These 
are quite discernible, even when within the tube; but if the 
somewhat difficult task of making a clean extract can be 
accomplished, the characteristics are more apparent. The 
somewhat bell-mouth top has a connection with the tube, but 
at the dissolution of partnership this is taken awa}'. During 
this process the threbble-headed ones droop their branches 
very much, and very often get fixed upon the nearest spine, 
like the legs of a fork. This is a position I have not yet 
observed in the round ones, but I have seen the heads of 
these fly off* and shoot through the water like a rocket 
