30 C. M. CHILD. 



irregular forms when they collapse at the time of operation. Cer- 

 tain parts of the margin at the cut end may roll inward to a 

 much greater extent than others, so that the cut surfaces on the 

 two sides of the body may fail to approximate at all and closure 

 cannot occur. The results of experiment are therefore less con- 

 stant and uniform than in C. solitarius, though in general similar. 



As regards the inrolling of cut margins in pieces of various 

 form, longitudinal and transverse strips, oblique pieces, etc., all 

 that has been said regarding C. solitaries (Child, 'o^d) will hold 

 for this species. Here, in fact, results may vary even more 

 widely than in C. solitarius because the body-wall is much more 

 flaccid in this species after collapse. It is possible to inhibit 

 completely the process of restitution simply by cutting the pieces 

 of certain shapes so that the inrolling of the body-wall will 

 prevent approximation of the cut margins : under these con- 

 ditions closure of the opening and formation of the missing parts 

 does not occur. 



The regional differences in the power of regulation are very 

 similar in the two species (cf. Child, '03^). The rapidity of oral 

 form-regulation decreases with increasing distance of the level of 

 section from the oral end. 



As regards the relations between size of the piece and regula- 

 tion the same similarity between the two species obtains. The 

 length of tentacles is distinctly not proportional to the size of the 

 piece (cf. Child, '03/^ Part II., pp. 3-6). In C. cBstiiarii the 

 uncertainty as to the size of minimal pieces is still greater than in 

 C. solitarius, because of the great irregularity in the process of 

 inrolling in short pieces. 



In neither species has the outgrowth of new tissue directly 

 from a free cut surface ever been observed (Child, '04^, pp. 

 66-74, Figs. 25-31 ; '04b, pp. 276-279, Figs. 3 and 4). On a 

 free cut surface of the body-wall exposed to the water scarcely a 

 trace of growth of new tissue appears and no restitution of the 

 missing parts. When, however, two cut surfaces or two parts 

 of a cut surface, e. g., the two margins of a fold at the cut end, 

 come into contact fusion occurs between them, but no further 

 growth takes place unless the region is subjected to tension pro- 

 duced by water in the enteron or in some other way. But when 

 the region is subjected to tension proliferation and growth occur 



