— 6 — 



In the region between southern California and Alaska the 

 average without the high range off southern California is 7°.3. 



Though undoubtedly future investigations will to some 

 extent alter these figures, yet it appears to be plainly indicated 

 that there is a progressive increase in the bathymétrie and 

 thermal range of the species of Florometra as one proceeds 

 northward from the Magellanic region, westward from Alaska, 

 and southward from the western Aleutian Islands. Corres- 

 ponding to this, and correlated with it, there is a marked 

 increase in the deviation from the average type of the genus, 

 first through individual, and later through both individual 

 and specific variation. 



Especially noteworthy is the great bathymétrie range off 

 southern California, and the great thermal range off southern 

 California and in the Gulf of Alaska. 



The Significance of the Facts brought out by a Study 

 of the Distribution of the Genus Florometra. 



The progressive increase in the bathymétrie and thermal 

 range, and in the coefficient of individual and specific varia- 

 bility, of the species of Florometra from the Magellanic region 

 northward, westward and southward clearly indicates the 

 origin of the genus in the Magellanic region, and its subsequent 

 extension north, west and south from that locality. 



The antarctic origin of Florometra is further confirmed by 

 the fact that all of the most closely related genera (Promacho- 

 crinus, Solanometra and Anthometra) are confined to the 

 antarctic regions. 



The life history of the comatulids shows that their distri- 

 bution can only be influenced by the conditions immediately 

 surrounding them. In perfectly stagnant water comatulids (or 

 stalked crinoids) would soon spread to all situations in which 

 the physical and economic conditions were such as to permit 

 of their existence. In the case of motion of the water immedia- 

 tely surrounding them they would naturally extend themselves 



