1908] Kofoid. — Exuviation and Autotomy in Ceratium. 381 



were lost prior to the renewed growth. The process and the 

 function served are, however, in many aspects similar to those 

 in typical regeneration. 



4. Regulatory nature of regeneration of the horns. — In both 

 of these types of regeneration or new formation of the horns, the 

 extensions of the horns exhibit the same kind of form regulation 

 as that which appears in normal growth. The proportions 

 characteristic of the species are maintained by the coincident 

 extension of both antapicals and of the apical also, in case it is 

 proportionately short at the time of regeneration. 



The regulatory character of the regeneration of the horns 

 after autotomy and independently of it is evident on inspection 

 of the table on p. 368. In nine of the fourteen cases of regenera- 

 tion all three horns regenerate together. The apical does not 

 exhibit this phenomenon in five instances and shows less growth 

 than the antapicals in all but three cases. In three of the four- 

 teen instances of regeneration the growth of the right horn exceeds 

 that of the left, in three cases it equals it, while in the remaining 

 eight it shows less growth. It appeai-s that the same causes 

 which control the extension of the horns in normal growth are 

 operative in the majority of instances to control their extension 

 in regeneration. 



5. Significance of regeneration. — It is obvious that increase in 

 the length of the horns, of those parts of the body in which the 

 number of units of surface per unit of volume, is greatest, results 

 in a relative increase of surface and a rise in the specific surface 

 of the organism. Increased specific surface is an adaptation of 

 flotation in water of higher temperature. Individuals in which 

 these extensions have occurred will be able to maintain their cus- 

 tomary location in the face of a rise in temperature up to a cer- 

 tain point, or to retain their position at given levels in warmer 

 waters into which they might move. The extent to which these 

 distal growths of the horns may be operative in adjustments of 

 capacity for flotation may be illustrated in the case of C. cali- 

 forniense. 



This specimen with renewed growth (figs. 32 and 33) was 

 taken May 28, 1904. 10 miles west of Pt. Loma over Cabral's 

 Banks in a haul from 75 fathoms. Surface waters on that day 



