NO. 19.] ECHINODERMS OF CONNECTICUT. 45 



in which such variations may be artificially produced. For if 

 the disk of a starfish of this species be cut between the bases of 

 two of the rays by an incision reaching from the border of the 

 disk to the mouth, one or two new rays may sometimes be pro- 

 duced in the healing of the wound. Such supernumerary rays are 

 at first smaller than the others, but it seems reasonable to assume 

 that by the compensatory regulations of the body they might 

 eventually become similar in all respects to the five original rays. 

 Some of the six- and seven-rayed individuals of the common star- 

 fish may have resulted from similar wounds inflicted by fishes or 

 by accident. In the removal of two or more rays, it sometimes 

 happens that the number regenerated is one less than the normal. 

 In this way a specimen like that shown in Fig. I may result. 



In Fig. 6 is shown a specimen in which it is apparent that 

 some injury has deprived the animal of all its rays except one; 

 the four lost members are being regenerated in their normal 

 positions about the disk. It is not at all unusual to find in- 

 dividuals which are thus replacing one or more rays which have 

 been lost by an injury. Such regeneration can be studied ex- 

 perimentally in the laboratory, and is discussed in the following 



chapter. 



Nevertheless it should be emphasized that, while certain 

 species from other parts of the world naturally reproduce by 

 spontaneous division, it is not believed that our native species 

 can do so. As stated in the following chapter, a single ray 

 without any portion of the disk cannot reproduce the missing 

 parts, and there is good reason for believing that a large animal 

 with even one or two rays removed is often destroyed by its 

 enemies before regeneration has taken place. In smaller in- 

 dividuals the injury caused by amputation seems less serious. 

 But it is only when protected by favorable conditions that the in- 

 jured starfish survives in the struggle for existence. 



REGENERATION 



It is said that many years ago, when the starfish first began 

 to be recognized as an important enemy of the oyster, the oyster 

 fishermen sought to wreak vengeance on these devourers by taking 

 such as came into the boat with the oysters, tearing them into 

 two parts and throwing both parts overboard. In how large a 



