SOME POINTS IN THE ECOLOGY OF EE CENT 

 CBINOIDS 



AUSTIN HOBART CLARK 



Although a considerable amount of work has been 

 done on the anatomy of various species of recent crinoids, 

 the embryology and development of two species, closely 

 allied, are well understood, and the systematic side of 

 the question lias received more or less attention, little has 

 been accomplished in the elucidation of the interrelation 

 of the crinoids and the other classes of marine inverte- 

 brates, or the relation of the crinoids to marine conditions 

 in general. This is undoubtedly due to the rarity of the 

 group, and its chiefly inaccessible habitat, rendering it, 

 as a whole, a difficult subject for extensive research; but 

 much may be learned from the data already recorded, and 

 it is the purpose of the present paper to suggest certain 

 lines along which much of interest may be done on the 

 basis of the present numerous, though scattered, records. 



It has long been known in regard to Antedon bifida of 

 the coasts of Europe that specimens taken in deep water 

 are larger than those taken in shallow water or along the 

 shore, though no plausible reason has been shown for 

 the phenomenon. It has been suggested that the coldness 

 of the deeper water may stimulate it to greater develop- 

 ment; but specimens from different localities, taken at a 

 considerable difference in depth, yet with the same bot- 

 tom temperature, will vary greatly, those from the greater 

 depth being much the larger; similarly, specimens from 

 the same depth, but with marked difference in the bottom 

 temperature, will be found to be of practically the same 

 size. As, however, specimens from very shallow water 

 are usually about 120 mm. in expanse, while those from 

 deep water are 220 mm. or more, it is evident that some 

 important factor is involved. 



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