NO. 19.] ECHINODERMS OF CONNECTICUT. 47 



the healing of the wounds and the regeneration of the missing 

 parts. 



Careful observations on this point which have been made by 

 Mead* show how rapidly these regenerative processes may occur 

 in the common starfish. 



The removal of a single arm has little if any influence on 

 the rate of growth of a young starfish, for such mutilated speci- 

 mens may grow as rapidly as normal individuals kept under 

 similar conditions. Futhermore the rate of growth of the re- 

 generating arm is on the average somewhat more rapid than that 

 of the remaining arms, so that there is a tendency to restore 

 the normal symmetry of the body. This is shown by the fact 

 that, of five individuals subjected to the experiment, the increase 

 in the length of the largest arm in each during about eight weeks 

 was 8, 10, 10, 11, and 10 mm., while the regenerating arm in 

 the same individuals grew 12, 1 1, 12, 11, and 9 mm., respectively, 

 in the same period. 



The removal of two arms in a young starfish likewise has 

 little if any effect on the rate of growth when food is abundant. 

 In such cases also an accentuated growth in the regenerating 

 arms as compared with the others illustrates again the com- 

 pensatory properties of the body. 



Although, as has been stated, it seems improbable that an 

 isolated arm can, in the common starfish, regenerate the missing 

 parts, yet the result is quite different if a small portion of the 

 disk is removed with the arm. In such cases, although growth 

 ceases for a long time, the normal body may eventually be 

 restored from the small portion of the disk remaining. 



Furthermore it is often possible to cut the disk with its at- 

 tached arms into two or more pieces and from each piece obtain 

 a perfect starfish. 



From such results it is conceivable that a starfish taken from 

 the water and torn roughly into two parts may, if a portion of 

 the disk remains attached to each part, eventually form two com- 

 plete animals by regeneration. That such an event is of usual 

 occurrence, however, is very improbable, because of the enemies 

 which may destroy the injured parts. It is far more likely that 



* Bulletin U. S. Fish Commission, vol. xix, 1899. 



