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POPULAR SCIENCE REVIEW. 
were deposited, and their remains are known as 66 stone lilies.” 
Now, however, they form an insignificant fraction of the existing 
representatives of the class, and the permanently stalked form 
( pentaci'inus ) is very rare, and confined to hot climes alone. 
These crinoids have the arms stellate, mostly branching. The 
ambulacral region is coextensive with the antambulacral region, 
the calix is distinct from the arms, the integument is calcareous, 
the generative organs are numerous and external, and the pri- 
mary larva is vermiform. The position of the body is the reverse 
of that in the echinus and star-fish, the mouth being upwards. 
Peculiar processes, termed cirri, project round the base of the 
calix in the free form comatula , and from the stalk, at intervals 
in the fixed and permanently stalked form pentacrinus. 
It is difficult to obtain good specimens of the Holothuridea , 
because these creatures have the singular habit, when alarmed, 
of “starting” so violently as to eject the whole of their viscera. 
Certain of the branching forms are also exceedingly difficult to 
procure in a perfect state, from the extreme facility and readiness 
with which they spontaneously break themselves up when cap- 
tured. The late Professor Edward Forbes gives a very amusing 
account of his unsuccessful attempt to secure a 66 brittle-star ” 
which he had caught in his dredge, and for which he had 
prepared a bucket of fresh water to kill it instantly, and so, he 
hoped, avoid its demolition. He says : “As I expected, a 
Luidia came up — a most gorgeous specimen. As it does not 
generally break up before it is raised above the surface of the 
sea, cautiously and anxiously I sank my bucket to a level with 
the dredge’s mouth, and proceeded in the most gentle manner 
to introduce Luidia to the purer element. Whether this cold 
element was too much for him, or the sight of the bucket too 
terrific, I know not, but in a moment he proceeded to dissolve 
his corporation, and at every mesh of the dredge his fragments 
were seen escaping. In despair I grasped the largest and brought 
up the extremity of an arm, with its terminating eye, the spinous 
eyelid of which opened and closed with something exceedingly 
like a wink of derision.” 
DESCRIPTION OF PLATE LXV.* 
Fio. 1. An echinus with the spino3 removed from one half of the shell so 
as to show — a, the ambulacral plates with their pores; i, the 
interambulacral plates; b, tubercles for the attachment of 
spines. 
• These figures are taken by permission from specimens which form part 
of Professor Flower's educational series in the Museum of the Royal College 
of Surgeons. 
