CARNIVOROUS UNSEGMENTED WORMS, &c. 153 



HEDGEHOG-SKINNED ANIMALS (ECHINODERMATA) 



The large and characteristic phylum of the Hedgehog-skinned 

 Animals, or ECHINODERMATA, to which Sea-Lilies, Feather-Stars, 

 Star-Fish, Brittle-Stars, and Sea-Urchins belong, does not include 

 a majority of carnivorous species. The most characteristic forms 

 in this respect are undoubtedly the Star- Fishes, of which the Com- 

 mon Star-Fish or Five-Finger (Uraster rubens) may be taken as 

 type. Crawling slowly along by means of the innumerable tube- 

 feet, which protrude from five grooves on the under side of the 

 body, the central mouth (from the neighbourhood of which these 

 grooves radiate) is from time to time brought into the neigh- 

 bourhood of some desirable bit of food in the form of a mollusc, 

 crustacean, or other animal. Then follows a process which re- 

 minds one of what takes place in a planarian worm, for while 

 the clinging body of the Star- Fish holds down the booty, a 

 large pouch-like stomach is protruded, which folds itself round 

 the desired object and, having enveloped it, is drawn back by 

 special muscles into the interior of its owner, where the process 

 of digestion is carried on. Star- Fishes appear to be among those 

 animals which do scavenging work, and Mr. Saville Kent is 

 inclined to think that this is part of their business in oyster- 

 beds, where they are usually believed to play havoc among the 

 inhabitants. Regarding them this author (in The Great Barrier 

 Reef of Australia) writes as follows: "Star-Fishes of all de- 

 scriptions, but more especially the ordinary five-rayed varieties, 

 Asteriadae, are universally held up for condemnation as repre- 

 senting the most insatiable foes of the oyster tribe. Whether 

 this wholesale condemnation is a just one there are some reasons 

 for doubting. In many instances it has been observed that the 

 star-fishes were merely acting as scavengers and preying on 

 dead or dying bivalves. The direct experiment was carried out 

 by the author some years since, in one of the large English 

 public aquaria, of keeping oysters and star-fish, including the 

 accredited most aggressive species, Asterias (Uraster] rubens, 

 in the same tank. The pre-supposed aggressors and their help- 

 less victims were thus maintained side by side in perfect health 

 for many months without a single instance occurring of molestation 

 of the oysters on the part of the star-fish. The Echinoderms, how- 

 ever, demonstrated their possession of normal healthy appetites 



