FORM REGULATION IN CERIANTHUS. 7 



illustrate this point. In general it may be stated that the rapidity 

 of regeneration in winter during the earlier stages is only about 

 one third of the rapidity in summer. 



The amount of regeneration as well as the rapidity also differs 

 with the season. During September and October regenerated 

 tentacles attained a length about twice as great as in similar pieces 

 during January and February. 



The length of time during which increase of size in regenerated 

 structures, e. g., tentacles, continues does not differ widely at high 

 and low temperatures, and since regeneration is less rapid it is 

 evident that the total amount must decrease with the temperature. 



The most interesting point in connection with the effect of 

 temperature on regeneration is the increase in size of the region 

 at the aboral end in which regeneration does not occur. During 

 the earlier months of my work the only pieces which failed to 

 regenerate were the aboral tips comprising about one eighth of 

 the body-length. Later, as illustrated in Series 45, an aboral 

 piece about one fifth of the body-length failed to regenerate. In 

 December, January and February pieces comprising more than 

 the aboral third failed to regenerate or showed only slight traces 

 of regeneration, as in Series $6B. Thus the portion of the body 

 incapable of regeneration increases as temperature decreases. 



In general, the effect of temperature upon regeneration in 

 Ccriantlms is what might be expected, since the activities of liv- 

 ing substance in general increase and decrease with the tempera- 

 ture. At high temperatures it is only the extreme aboral end 

 which cannot regenerate typically. From this " inactive " region 

 regenerative power increases toward the oral end. As the tem- 

 perature falls the limit of " inactivity " must advance toward the 

 oral end, and more and more of the body be included in it. 



The Number of Regenerated Tentacles. 



It was determined that the number of tentacles regenerated is 

 always less than the original number, and furthermore, that it 

 decreases as the distance between the oral end of the piece and 

 the oral end of the body increases. 



It is difficult to determine with certainty the number of ten- 

 tacles in living specimens of C. solitarius, but in fixed material 



