62 Animal Life by the Sea-shore. 



development of the arms, Avhich are scarcely defined from the 

 disc, the whole animal being of an almost pentagonal shape. 

 When alive this starfish is usually of a greenish yellow, some- 

 times tinged with red. 



Solasler papposus is an inhabitant of deeper water, but is 

 sometimes cast ashore ; it differs from the forms already 

 mentioned in having an increased number of arms, viz., twelve 

 to fifteen (frontispiece). 



Starfishes are omnivorous creatures with distinct pre- 

 daceous tendencies, and their partiality to bivalve molluscs 

 is only too well known to oyster-growers, whole beds ot these 

 valualjle shellfish having been destroyed in one night by an 

 invasion of Asterias. The suctorial feet are the chief instru- 

 ment used to open bivalve shells ; the finger-like arms embrace 

 the shell, and the suckers exert a steady pull on both valves 

 until the muscle of the mollusc relaxes, when the contents are 

 engulfed by the sac-like stomach, which the starfish is able to 

 evert through its mouth. Starfishes are endowed with remark- 

 able powers of self-mutilation and regeneration ; one or more 

 of the arms can be cast off and regrown, and this accounts for 

 specimens being often found with the arms of unequal size. 

 Even a detached arm is capable of producing buds which grow 

 into a complete nidividual. Wliile probably originally a 

 deAdce for escaping from enemies, like the fragile tail of lizards, 

 tills self-mutilation has become, in some forms, a second mode 

 of reproduction, supplementing the normal, which is by eggs. 

 Most starfishes have separate sexes. 



The Brittle-stars (Ophiurids) bear a certain resemblance 

 to the starfishes, but this resemblance is very superficial ; they 

 belong to a quite different group of Echinoderms. The body is 

 likewise divisible into disc and arms, the latter, however, being 

 narrow and perfectlj^ distinct from the circular disc ; they are, 

 moreover, solid, not containing any part of the gut, and lack 

 the suctorial feet, the flexible arms themselves being the 

 locomotory organs. The vent, as distinct from the mouth, is 

 absent, another important difference as compared with true 

 starfishes. A considerable number of different kinds of Brittle- 

 stars occur on our coasts ; one is here figured (frontispiece) as a 

 characteristic example, Ophioihrix fragilis. 



In the Echinoderms known as Sea-urchins or Sea-eggs, 

 the plates of the skin attain their highest development. Large 

 and thick and interlocking with one another, they constitute a 

 continuous and rigid box or shell, which, it may be mentioned, 

 has nothing in common with the shell of a mollusc, being a part 



