STAK-FISHES. 177 



bottom of the digestive sac by a free aperture ; the contents of this 

 organ, moreover, resemble bile both in taste and colour*. 



(464.) In the slender-rayed genera, such as Opliiura, the caecal 

 appendages are not met with ; but their deficiency appears to be sup- 

 plied by the plicated walls of the stomach itself, the numerous folds of 

 which resemble lateral leaflets attached to the central cavity. We are 

 unacquainted with the precise organization of the alimentary canal in 

 Comatula ; but, from the orifices visible in the shell, it would appear 

 that in this genus, as well as in some Crinoid species, the digestive tube 

 was furnished with an anal aperture. 



(465.) The Star-fishes, grossly considered, might be regarded as mere 

 walking stomachs ; and the office assigned to them in the economy of 

 nature, that of devouring all sorts of garbage and offal that would 

 otherwise accumulate upon our shores. But, as we have already seen, 

 their diet is by no means exclusively limited to such materials, since 

 crustaceans, shell-fish of various kinds, and even small fishes, easily 

 fall victims to their voracity. Delle Chiaje found a human molar tooth 

 in the stomach of an individual which he examined. Neither is the 

 size of the prey whereon they feed so diminutive as we might suppose 

 from a mere inspection of the orifice representing the mouth ; for not 

 only is this extremely dilatable, but, as we have found to be the case in 

 the Actiniae, the stomach is occasionally partially inverted, in order 

 more completely to embrace substances about to be devoured. Shell- 

 fishes are frequently swallowed whole ; and a living specimen of Chama 

 antiquata, Linn., has been taken entire from the digestive cavity of 

 an Asterias. It appears, moreover, that it is not necessary for testa- 

 ceous mollusca to be absolutely swallowed, shells and all, to enable the 

 AsteridaB to obtain possession of the enclosed animal, as they would 

 seem to have the power of attacking large oysters, to which they are 

 generally believed to be peculiarly destructive, and of eating them out 

 of their shells. The ancients believed that, in order to accomplish this, 

 the star-fish, on finding an oyster partially open, cunningly inserted 

 one of its rays between the valves, and thus gradually insinuating 

 itself, destroyed its victim f. Modern observations do not, as far as we 

 are aware, fully bear out the above opinion of our ancestors as to the 



* Delle Chiaje. 



f This may be gathered from Aldrovandus, who writes as follows : " Alii ostre- 

 arum hostes sunt Stellas marinae molli crusta intectaj,vero tarn crude! iter (ut ^Elianus, 

 lib. ix. cap. 22, ait) inimicae ut has ipsas exedant et conficiunt. Ratio insidiarum 

 quas eis moliuntur ejusmodi est. Cum testacea suas patefaciant conchas, cum vel 

 refrigeratione egent, vel ut aliquid pertinens ad victum incidat ; eae, uno de suis sive 

 cruribus sive radiis intra testas ostreae hiantis insito eas claudi prohibente, carne 

 implentur " (Testae, lib. iii. p. 487). Thus likewise Oppian : 



" Sic struit insidias, sic subdola fraudes 

 Stella marina parat, sed nullo adjuta lapillo 

 Nititur, et pedibus scabris disjungit hiantes." 



