46 ON THE COMMON BRITTLE STAR. 
So in the present case, the hooks disappeared when the rays 
furnished with long spines are matured, and the flat fan-shaped 
spines are doubtless modified by further deposits, so as to assume 
the mature form. 
I have just said ‘the hooks disappear,” but how is this accom- 
plished? Here was a difficulty that beset me, and well nigh 
remained unsolved. Luckily I boiled a moderate-sized specimen 
in liquid potash, to procure some “hooks,’’ from which to make 
the necessary sketches, and by this means, I obtained a plentiful 
supply, and at the same time ascertained, to my complete satis- 
faction, the reason of the claws not being present in mature 
specimens. ‘This is so extremely interesting, that I have figured 
some of the most striking features, and can best explain the 
process in conjunction with these figures. 
Figs. 5 and 6 represent two fully formed and perfect hooks, the 
former having one fang (in addition to the tip) and the latter 
two; this form may be taken as the most perfect stage of the 
organ as a hook. 
If Fig. 7 is now examined, it will be seen that there are irregular 
little notches on the upper outer margin, still more decided in Fig. 
9, this specimen having lost much of the character of a hook. 
Fig. 8 shows the peculiar “‘set’’ of the deposit in growth; which 
by means of a considerable increase of calcareous material at one 
particular part, shows the commencement of a longitudinal growth, 
eventually producing a deposit of a spinous character. 
In Fig. 10 the character of a hook is changed, a stumpy spine 
being the result of a successive growth, both from the base, and 
also by an irregular deposit at the margins. 
In Figs. 11 and 12 (still further growths) the distinctive characters 
of the hooks are just visible; these figures may be considered repre- 
sentations of regular spines, ‘“‘ long and jagged.” 
These specimens are of peculiar interest, in proving that the 
growth of these organs, is not only by means of a gradual deposit 
of calcareous material on their external surfaces, but also, by a 
regular “growth” from the base. If this were not the case, the 
tip of the hooks would be left far down, or near the base, and 
would not be carried or pushed forward. That this is so 
