48 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [BuU. 



the part having the greater portion of the disk will quickly re- 

 generate its missing organs, while the other part will perish. 



The regenerative capacity of the northern starfish, Asierias 

 vulgaris, has been the subject of an extensive series of ex- 

 periments by Dr. Helen D. King.* In this species, as in the 

 common starfish, a single arm without any portion of the disk 

 may live for several weeks, but is unable to reproduce the missing 

 parts of the body. 



Of nearly two thousand individuals of this species examined, 

 about eleven per-cent showed one or more arms in process of 

 regeneration. In all cases except one the regeneration involved 

 the production of one or more new arms from the disk, and not 

 a repair of the injured tissues of an arm. It is thus assumed that 

 a badly injured arm is in nature thrown off and replaced by a 

 new one. 



When the tip of an arm is removed, however, regeneration 

 of a new tip occurs, and the new eye-spot may be formed within 

 a week after the operation. The regeneration of a complete arm 

 from the disk requires several months. 



When the arms are split longitudinally they are always 

 thrown off, except when the tip alone is split. In the latter case 

 two new tips may develop, giving a forked extremity to the arm. 

 Oblique cuts and the removal of small pieces result in the normal 

 regeneration of the injured tissues. The wounds made by cut- 

 ting the disk may lead to the formation of supernumerary arms, 

 as described in the preceding chapter. 



REPRODUCTION 



The starfishes are of separate sexes, although there are no 

 external characters by which the sex is indicated. 



One of the chief reasons why the starfish occurs in such 

 enormous numbers, is found in the immense number of eggs 

 produced by a single femiale. The animals are capable of breed- 

 ing, as has been recently found by Mead, if the food supply is 

 abundant, when but one year old. As the animal increases in 

 size during succeeding years, an increasing number of eggs or 

 sperm cells are produced annually. 



* Archiv fiir Entwickelungsmechanili, vol. ix, pp. 724-737, 1900. 



