ON THE COMMON BRITTLE STAR. 45 
under side ; but where are the flat spines and claws as seen in 
a young form ?—none are visible; examine every large specimen 
that you can obtain, and this will be found to hold good. 
It would therefore appear, that the claws are formed to assist 
the young animal in attaching itself to various bodies on which 
it is found, and also for the purpose of locomotion: this can 
easily be understood; but why the flat form of spines should in 
the first two or three instances precede the regular form, I am 
unable to say: the extraordinary part being, that these flat forms 
‘are only produced in early growth, and not (as far as I have seen 
in the many specimens examined), when the rays begin to 
lengthen; the long form being the only kind then met with— 
still, however, preceded by the claws. 
This is shown at Fig. 3, a portion of a ray—the extremity only 
being shown: the claws here greatly preponderate in size over 
the spines, which are just appearing. 
This also holds good in the case of reproduced rays—an ex- 
ample may be cited. A Brittle Star now before me, measuring 
34 inches from tip to tip, has a small ray, only half an inch long, 
about half of which is old, the remainder being of much smaller 
dimensions, and in course of reproduction: the latter is seen to 
possess claws, and the long jagged spines of small size along the 
newly-produced part; but not a sign of a claw upon the old por- 
tion ; even the first two joints of the new are also without them. 
Sars alludes to the temporary acquisition of organs to be sub- 
sequently dispensed with, as others more in character with the 
animal are produced, when he says, in speaking of the develop- 
mental part of their history, ‘‘ Furthermore parts are developed, 
for instance the above-mentioned organs of attachment, which are 
destined only for immature age, and therefore disappear entirely 
as the animal approaches to maturity. The reason for the dis- 
appearance of the organs of attachment depends upon their be- 
coming utterly useless, on account of the development of tentacles 
with which the young star-fish begins a new method of locomo- 
tion, and enters into other relations with the external world.”’* 
* On the development of Star-fishes by M. Sars in Annals and Mag. Nat. History.—Oct., 
1844, 
WO ig Wig EARS 1G aig 
