FORM-REGULATIONS IN CERIANTHUS. 28 / 



In cases of aboral duplication each part is really a " half," but 

 the aboral pore is duplicated, each pore being formed from a part 

 of the old pore in case the cut passed through it, or one pore 

 being formed anew in case the cut passed more or less to one 

 side of the old pore. 



The varieties in method of closure in these cases are almost 

 infinite as may be conceived from the discussion of inrolling in a 

 previous paper (Child, '04;?). Scarcely any two of the resulting 

 forms are alike but the many differences in detail do not acid essen- 

 tially to our knowledge, being merely illustrations of one general 

 principle. They do show very clearly, however, how little power 

 the animal possesses to maintain or return to a particular form after 

 section. All is pure chance in the matter of closure. Whatever 

 portions of the cut surfaces come into contact unite. The ten- 

 sions due to internal water-pressure may serve in some cases to 

 modify the peculiar forms, but in other cases this does not occuiv 

 All depends upon the conditions of the particular case. 



In cases where closure and duplication of the oral or aboral 

 ends is accomplished I have never seen reduction, absorption, or 

 loss by constriction of one of the two parts afterward. Occa- 

 sionally if the duplication involves merely the extreme end it 

 gradually disappears ; the two halves gradually becoming a 

 whole. In other cases where the duplication extends for some 

 distance from the end so that the two parts are distinct, I have 

 not noted any changes which might be interpreted as a regula- 

 tion of the atypical form, although specimens of this kind have 

 been kept for more than three months. 



There is, no doubt, that many other varieties of monstrous 

 forms may be produced. The only obstacle is the frequent 

 separation of parts from the body after severe operation. 



SUMMARY. 



I. Regeneration in Ceriantliits is not proportional to the size 

 of the piece. The smaller the piece, other conditions remaining 

 the same, the greater the relative amount of regeneration. As 

 regards absolute amount of regeneration the small and large 

 pieces are at first alike, but later the small piece falls behind, /. e,, 

 regeneration is retarded and ceases sooner than in the large 

 piece, probably owing to lack of available energy. 



