140 ECHINODERMS OF THE BRITISH ISLES 



reddish ones and have been regarded as a separate species {Ast. 

 violacea) ; but as no definite distinguishing character appears to 

 exist, and all transitions in the coloration may be found even in 

 one and the same locality, they are no doubt all one and the same 

 very variable species. Abnormalities with 4 or 6, or even 7-8 (9), 

 arms, and also such as have two- or three- branching arms, are 

 not rare. 



The breeding season is in summer, from April to July, or 

 perhaps even later. The larva has a Brachiolaria stage (Fig. 28, 4) ; 

 it may in places occur in enormous numbers in the plankton. 

 The young sea-stars may especially be found in numbers on the 

 Zostera leaves, feeding mainly on young Mytilus. The rate of 



Fig. Id.^Asterias rubens. Dorsal side. Nat. size. 

 (From Danmark''s Fauna.) 



growth depends on the amount of food available ; with rich food 

 they grow very rapidly (cf. p. 48). Sexual maturity is reached 

 in the course of one year. 



It is a very voracious animal. Its food consists especially of 

 molluscs ; larger prey it digests outside the body by evaginating 

 the stomach over it. (Concerning the way in which it opens 

 larger mussels, cf. above, p. 47, Fig. 29.) But it also eats 

 crustaceans (especially barnacles), worms, echinoderms, even 

 specimens of its own species, indeed almost everything eatable, 

 living or dead. It does considerable damage to oyster-cul- 

 tures, though it would appear that it cannot by itseK open the 

 larger, undamaged oysters. At Plymouth it is reported to feed 

 mainly on Pecten opercularis. Fishes it cannot take, except when 

 caught in nets ; but it may well cause some damage to the fishes, 

 injuring them with its spines on being pressed together in 



