124 Papers from the Department of Marine Biology. 
Mr. Clark says (p. 606) that very large species of ‘‘Comasteride 
occur abundantly im very shallow water, often just below the low-tide 
mark’ in the tropics. This is apparently true for Maér, though it is 
not clear what Mr. Clark would call “very large.’’ But when he says 
that the individuals “decrease in size with depth,” doubt may well 
be felt. Of course, when a depth sufficient to diminish the amount of 
vegetable plankton is reached comatulids very possibly become fewer 
and smaller. No crinoids were taken at Maér at a depth sufficient to 
throw any light on this point. It is certainly true at Maér, as Mr. 
Clark goes on to say, that ‘‘the beaches and rocky shores warm up, to 
be covered again at high tide with comparatively cool water full of 
organisms,” but when he adds the words ‘‘unable to stand a great 
change of temperature,’’ we may well ask for evidence. On the reef 
flats at Maér we found that many organisms living in the area where at 
low tide the water became heated were able to thrive within wide limits 
of temperature. Moreover, as the cold water of the incoming tide 
comes over the flat, it is not appreciably raised in temperature, but 
brings down to its own degree the water, rocks, and sand which have 
been heated. There was never the least evidence of the destruction of 
pelagic life on the reef flat due to heat. But even granting that such 
a destruction does occur, why should Mr. Clark say it would be ‘‘swept 
back into the sea, to fall just beyond the low-tide mark?” Would it 
not be just as probably washed up on the beach, dropped on the reef- 
flat, or carried far out to sea by the receding tide, as deposited just 
below low-tide mark? 
In conclusion, on this subject of the food of crinoids, the legitimate 
criticism of Mr. Clark’s views may be summed up in this way: While 
there need be no quarrel with his assumption that a big food-supply 
will give rise to big crinoids, as there certainly is such a factor in the 
growth of some species of starfish, it must not be forgotten that it is 
after all only an assumption. When to this he adds the assumption 
that animal food, especially in the form of a hypothetical ‘rainfall of 
carcasses,” is the fundamental factor in accounting for the distribution 
of big crinoids, we may well become exceedingly skeptical, since the 
evidence obtained at Maér shows that the comatulids are vegetable 
feeders, and live in such positions that no “‘rainfall”’ of food could 
readily reach them. Finally, the assumptions, by which he attempts 
to account for the existence of the hypothetical “‘rainfall of carcasses”’ 
in the various regions where the size of the crinoids seems to require 
it, appear to be as dubious as they are ingenious. While fully recog- 
nizing how limited our knowledge of crinoids is, we are obliged to 
maintain that there are few facts known which give any support to 
Mr. Clark’s conclusions. 
In his discussion of the colors of crinoids, Mr. Clark has a much 
better basis of fact, but here too he makes certain assumptions that 
