Vol. VIII. April, lyos. No. 5. 



BIOLOGICAL BULLETIN 



FORM-REGULATION IN .CERIANTHUS, IX. 

 REGULATION, FORM, AND PROPORTION. 



C. M. CHILD. 



REGENERATION AND PROPORTION. 



In the second paper of this series (Child, '03$) attention was 

 called to the fact that the amount of regeneration is not propor- 

 tional to the size of the piece. Small pieces above a certain 

 limit regenerate as rapidly as pieces many times their size up to a 

 late stage. Finally the small pieces fall slightly behind those of 

 large sizes, probably as was suggested, because of the exhaus- 

 tion of the material available for regeneration under the partic- 

 ular conditions (relative exhaustion, Child, '03$). Evidently the 

 exhaustion will occur earlier, other conditions remaining the 

 same, as the size of the piece decreases. Consequently there is 

 some difference in the amount of regeneration according to the 

 size of the piece, but this difference appears only at late stages 

 and is very much less than the difference in size between the 

 pieces. In other words the regenerated structures of small 

 pieces are always relatively larger than those of large pieces. 



The two series 54 and 55 which were described fully in my 

 second paper (Child, '03$) illustrate this fact so well that it is 

 desirable to recall certain points in this connectio.n. 



In the preparation of the two series the disc and oesophagus 

 were removed by a transverse cut just aboral to the oesophagus 

 and then the remaining portion of the body was cut into two 

 pieces A and B. In Series 54^ the oral piece was about four 

 times as long as B at the time of section, while in series 55 the 

 aboral piece B was about four times as long as A. Ten speci- 

 mens were used for each series. In the pieces A of the two 



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