CHAP. 1X. ] THE DEEP-SEA FAUNA. . AAD 
A young specimen of P. wyville-thomsoni gives the 
mode in which this freedom is acquired. The total 
length of this specimen is 95 mm., of which the head 
occupies 835 mm. ‘The stem is broken off in the 
middle of the eighth internode from the head. The 
lowest complete internode consists of 14 joints, the 
next of 18, the next of 20, and the next of 26 joints. 
There are 8 joints in the cirri of the lowest whorl, 
10 in those of the second, 12 in those of the third, 
and 14 in those of the fourth. ‘This is the reverse of 
the condition in adult specimens, in all of which the 
numbers of joints in the internodes, and of joints 
in the cirri, decrease regularly from below upwards. 
The broken internode in the young example, and 
the three internodes above it, are atrophied and un- 
developed, and suddenly at the third node from the 
head the stem increases in thickness, and looks as 
if it were fully nourished. There can be no doubt 
that in early life the crinoid is attached, and that it 
becomes disengaged by the withering of the lower 
part of the stem. 
The structure of the cup is the same as in P. 
asteria and P. miillert. The basals appear in the 
form of slield-like projections crowning the salient 
angles of the stem. Alternating with these we have 
well-developed first radials, forming a closed ring 
and articulating to free second radials by muscular 
joints, The second radials are united by a syzygy 
to the radial axillaries, which as usual give off each 
two first brachials from their bevelled sides. A 
second brachial is united by syzygy to the first, 
and normally this second brachial is an axillary, 
and gives off two simple arms; sometimes, however, 
