4 C. M. CHILD. 



at the final stage of the experiment when it was seen that 

 the smaller pieces were falling behind the larger pieces with re- 

 spect to size of the regenerated structures. In Series 35 the 

 possible effect of size upon the final result was noted, but here 

 also there was no visible effect during the earlier stages. 



The results afforded by these two series are confirmed by a 

 large number of experiments. In no case, when pieces were 

 above a certain minimal size, could any effect of size upon rapid- 

 ity of regeneration be observed during the earlier stages. In the 

 later stages it was found that regeneration became less rapid and 

 ceased in the smaller pieces earlier than in the larger. Even in 

 this respect differences were slight in pieces of widely different 

 size. 



The amount of regeneration is then not proportional to the 

 size of the piece. As regards both oral and aboral cut surfaces 

 smaller pieces show a relatively much greater amount of regen- 

 eration than larger pieces ending at the same level. In a piece 

 one tenth the length of the body the tentacles regenerate at first 

 with the same rapidity as in a piece nine times as long. Only 

 after the tentacles are well formed and several millimeters in 

 length does a difference appear. In many pieces so short that 

 they appeared to consist only of the regenerated disc and ten- 

 tacles these organs were of the same size up to a late stage as in 

 pieces many times as large. 



As regards the nature of the effect of size in regeneration in 

 CeriantJms and in many other forms a few points which have 

 suggested themselves to me may be discussed in the hope of aid- 

 ing in the analysis of this phase of the problem. It may be 

 stated as a general rule that as regeneration advances the stim- 

 ulus to regeneration diminishes. We may suppose that a certain 

 amount of material or energy is necessary for the production of 

 regenerated structures of a certain size. This energy is derived 

 from the substance of the body in cases like the present where 

 no food is supplied. The smaller pieces possess of course a 

 smaller amount of material or energy available for regeneration. 

 This is sufficient, however, for the earlier stages, but as the 

 amount diminishes it is probably given up less readily by the 

 other tissues. The well-known regulative power of animal tis- 



