The Comatulids of Torres Strait. 123 



The two questions which arise in connection with this original theory 

 are : first, is there such a rainfall of carcasses? and, second, if there were, 

 would the crinoids use it for food? In regard to the existence of such 

 a "rainfall of carcasses," there is room for some skepticism. Pelagic 

 microorganisms appear to live (except when overtaken by some sudden 

 catastrophe covering a wide area of sea) until eaten by some larger 

 organism. There is little evidence that they die of either disease or 

 old age. The material collected by tow-nets, both at the surface and 

 at more or less considerable distances below it, usually contains a 

 surprisingly small amount of dead material (excluding of course dust, 

 sand, chaff, etc., from the shore). 



Mr. Clark recognizes the necessity of some special cause for the 

 slaughter of the microorganisms and finds it in the decreasing of the 

 salinity of the sea-water by supplies of fresh water from melting ice, 

 flooded streams, and torrential rains. With regard to melting ice, 

 he offers the following illustration: "The west coast of Greenland 

 abounds in fjords which are continually giving off fresh-water ice, 

 which floats off melting as it goes, thereby killing millions of small 

 organisms which are unable to endure a great change in the salinity 

 of the medium they inhabit." If the fresh-water ice is "continually" 

 given off, it is hard to see how the salinity of the sea thereabouts can 

 undergo any "great change." Moreover, how about the long Arctic 

 winter, when there is practically no ice movement out of the fjords? 

 The intermittent and uncertain appearance of floods and torrential 

 rains seems to render them very improbable factors in the wholesale 

 death of the plankton, although it is quite possible that occasionally 

 they may play the part that Mr. Clark demands of them. 



But even granting the "rainfall of carcasses," there is no evidence 

 that it would serve as food for the comatulids among which it fell. 

 Judging from the observations at Mae'r, comatulids live and thrive only 

 where conditions permit a very rich vegetable plankton to swarm in 

 the water. Where such a plankton exists, no amount of animal matter 

 added to it, either dead or alive, will greatly affect the comatulid's 

 food. Moreover, crinoids, at least comatulids, do not live lying ex- 

 posed, oral side up, on the open bottom of the sea, but are concealed 

 under rocks with the oral side down, where a rainfall of carcasses or of 

 other food would scarcely reach them at all. Or they live among 

 corals and sponges, so protected that very little of such a supposed 

 rainfall would ever reach them. 



Of course, the observations made at Mae'r are exceedingly few and 

 deal with a small number of species, in a very limited area, but they 

 are almost the only facts that have yet been published on the subject. 

 On a priori grounds, deep-sea crinoids living below the limit of vege- 

 table life must be animal feeders, but as yet we know nothing as to the 

 composition of the food, and there is no reason to suppose it consists of 



"carcasses." 



