492 C. M. Child 



is usually not as violent as in the above cases and the enteric or- 

 gans are extruded only slightly and temporarily, or not at all. In 

 these cases restitution is complete at the same levels at w^hich it is 

 impossible in pieces with both ends cut, though the physiological 

 capacity may be the same or almost the same in both. 



The non-teleological character of the regulatory reactions fol- 

 lowing removal of a part appears very clearly in these relations. 

 In the regions where the body is physiologically capable of com- 

 plete restitution, even in small pieces, the physical conditions 

 resulting from the wound interfere with and prevent restitution 

 in certain cases. In the extreme aboral region, on the other hand, 

 where the physiological capacity for restitution is very slight no 

 such physical obstacles to closure of the wound exist. 



2 The Experimental Data 



Regional Difference in Rapidity and Amount of Restitution 



As was noted above, the presence or absence of the oesophagus 

 determines to a certain extent the method of wound-closure and 

 the time at which the restitution proper may begin. This, how- 

 ever, is merely an incidental anatomical factor: another regional 

 factor more fundamental in character and quite independent of 

 the oesophagus exists, as is evident from the decreasing rapidity 

 of restitution with increasing distance from the oral end. 



The time of appearance of the tentacles and the rapidity of their 

 growth are the most conspicuous features of this regional differ- 

 ence. Measurements of the length of the tentacles cannot ot 

 course possess any exact value for the length of the tentacles varies 

 within wide limits according to the degree of distension. In 

 individuals kept under similar or identical conditions, however, 

 the degree of distension is likely to be more or less similar, and 

 observation and measurement of a large number of individuals 

 have shown very clearly that a comparison of tentacle-lengths is 

 possible. Such measurements do not show anything that cannot 

 be discovered by direct observation; they merely afford a means 

 for recording briefly the results of observation. 



