376 University of California Publications in Zoology. [Vol.4 



portionately greater distance from the nucleus than they are in 

 colder waters. The contrast in length of horns of Ceratium from 

 tropical and arctic watere has been a matter of frequent comment 

 (see Chun '02) and the principle of the correlation of the pro- 

 cesses of pelagic organisms with the function of flotation has often 

 been noted [see Wesenberg-Lund ( :00) and Ostwald (:03)]. 

 Temperature thus bears a definite relation to the distance from 

 the nucleus to which the horns of Ceratium may extend. In high 

 temperatures this distance is greater than at low ones. So also 



Fig. 25. — Ventral view of a normal Ceratium arcuatwn. X 155. 

 Fig. 26. — Ventral view of another individual after distal autotomy of the 

 tips of the antapicals. X 160. 



in the fully grown organism it may follow that the distance in 

 the horn to which the normal processes of metabolism can be 

 maintained is in a similar manner atfected by temperature. A 

 long-horned Ceratium entering a region of cooler water suffers, 

 it may be, a reduction in the radius of action of nuclear activity 

 and autotomy of a regiilatory character follows. The sugges- 

 tion naturally arises that under conditions of lowered tempera- 

 ture a ferment is produced or becomes effective which brings 

 about a resolution of the wall and that the temperature regulates 



