HARDWICKE'S SCIENCE-GOSSIP. 



zoophyte-trough filled with sea-water, and we can 

 thus study it in its living state, which is highly im- 

 portant with delicate structures, such as that we 

 have in hand. The ambulacra are separated from 

 each other by peculiar thin curved calcareous plates, 

 but of considerable width, which are placed side by 

 side all down the under surface of the rays, and 

 from the bottom of the avenues. Between these 

 plates the fleshy arms protrude themselves : now, 

 on cutting open the ray we see that in the interior 

 side of these plates the arms swell out into trans- 

 parent bulbs filled with sea-water. It is by the 

 contraction of these bodies, forcing, as they then 

 do, the water into them, that the ambulacra are 

 expanded, and on the retraction of the suckers the 

 water is sent back again into the bulbs. 



The spaces between the calcareous network are 

 covered with a transparent skin, which can be 

 protruded in the form of a short tentacle. Within 

 these tentacles, which are very transparent, violent 

 vortices are produced by the cilia lining the interior, 

 and whirling round clouds of alimentary particles. 

 It is difficult to conjecture what may be the object 

 of these processes ; but from their protrusion and 

 retraction, and being covered and lined with cilia, 

 they are probably connected with respiration. They 

 are distributed all over the upper side of the star- 

 fish, and when protruded (which they can be to the 

 eighth of an inch in a full-sized specimen) give to 

 the animal a peculiar gauze-like appearance. 



Interspersed amongst the tentacular bodies, and 

 generally near the spines, are the pedicellarisc, pe- 

 culiar pincer-like structures, which are constantly 

 opening and shutting during the life of the animal, 

 and of which a great deal has been written, but 

 without any great results : the fact of their not 

 communicating with the interior of the body of the 

 animal has made their object in the economy of the 

 star-fish extremely difficult to imagine. They have 

 been thought by some to be parasites ; but there 

 is not the least doubt now, of their belonging to and 

 being part of the animal. These bodies are very 

 numerous in large specimens, particularly towards 

 the sides of the rays, and are often absent in young 

 ones. In this state Porbes says it is the Asterias 

 clathrata of Pennant. Around the spines princi- 

 pally, but sometimes in isolated groups, are placed 

 other and very remarkable structures. The investing 

 skin of the animal rises up into mounds, which 

 divide at the top into short tubular processes, each 

 of which ends in a curious opening, like the mouth 

 of a fish. The jaws are formed of hard calcareous 

 matter, transparent like glass, and are broad and 

 short, very unlike the pedicellariae, which are nar- 

 row and long. These mouths are constantly 

 opening a little, and closing again. There appears 

 to be a passage from them down into the interior 

 of the body. I have not seen these curious 

 structures described before, although to me they 



seem quite, if not more important, than the 

 pedicellariae, and are much more numerous, there 

 being generally twenty or more around each spine. 

 They are very plentiful near the avenues, where 

 also the pedicellariae are most abundant Might 

 not the use of the latter be to hold substances to 

 attract swarms of infusoria which might then be 

 taken in with the water by the " fish-mouths," and 

 serve as food for the star-fish in the absence of re- 

 gular food by the mouth ? Constant observation 

 of the living animal under the microscope seems to 

 be the only way of solving this difficult question. 



At the top of each ray, and surrounded by spines, 

 is a red spot, consisting of a number of ruby cells 

 in a group. This has been called their eye ; but 

 whether it is endowed with the sense of vision is 

 uncertain. It is the only known organ of sense in 

 the star-fish, and seems particularly used when the 

 animal is searching for food ; it then always keeps 

 the tips of the rays turned up, exposing well this 

 red spot. 



The animal is moderately lively, and will often be 

 seen walking rather faster than a snail. On the 

 sea-coast it seems fond of clinging to the under 

 sides of ledges. At some seasons it is not common, 

 only one or two being seen thrown up by the tide; 

 this more especially in winter. I have seen it in 

 warm weather in great abundance, and this after 

 calm seas. It appears very sensitive to change of 

 temperature; the star-fish in my tank always 

 seeking the deeper parts on the setting in of cold 

 weather ; those parts being then of course warmer 

 than the surface. 



This species is very voracious, and will eat almost 

 any animal matter. Its manner of feeding is as 

 follows : It is perhaps walking on a piece of rock, 

 turning up the ray-tips and exposing the red " eye " 

 spots, as I before remarked. Should there be a 

 piece of fish or dead worm near, it is soon discovered 

 and drawn by means of the suckers towards the 

 mouth; the body is now raised up to admit the 

 substance, and the rays clasp round it. The body 

 is now much inflated with water, and the stomach 

 is turned out like a transparent bladder, completely 

 enveloping the food ; if not too large, it is perhaps 

 drawn quite into the body, there to undergo di- 

 gestion, and is>ejected in a day or so in a finely- 

 divided granulous condition. 



In colour this species is very variable, passing 

 from pale lemon down to dark brick-red or violet ; 

 in this state having much in common with TJraster 

 violacea ; and it is often difficult by this means to 

 define the two species. 



Porbes seems to question the suicidal propensi- 

 ties of this animal ; but there is no doubt of its 

 ability to throw off its rays. I have seen an animal 

 break off all its rays till nothing but the disk was 

 left. This is certain to happen if the star-fisb is 

 placed in an ill -aerated aquarium. This habit I 



