106 STAEFISH GALLERY. 



THE STAEFISH GALLEET. 



In the Staefish Galleey is exhibited a series of the animals 

 belonging to the class Echinodenna ; of these the Starfishes are the 

 best known, while others are the Sea-Lilies, Sea-Urchins, and Sea- 

 Cucumbers or Sea-Slugs (Wall-case IV.). 



A small collection of various kinds of Worms is also exhibited in 

 this Gallery (Wall-cases I.-III.). 



EOHINODEEMA. 



Six table-cases contain the dried Echinoderms arranged in 

 systematic order. The seventh is devoted to preparations, models, 

 and figures illustrative of the structure and life-history of various 

 members of the group. 



An inspection of that Case and the accompanying woodcuts will 

 make clear the distinctive characters of the Echinoderma. Unlike 

 that of a Crayfish or a Mussel, the body does not appear to be divided 

 into two equal or symmetrical halves, though it really is ; this is due 

 to the possession of a number of rays, of which there are ordinarily 

 five. The skin is strengthened by the deposition in it of carbonate 

 of lime, which may be in the form of continuous plates or bars, 

 or of separate scattered spicules, A series of tube-feet or suckers 

 (podia) are generally developed along each ray, and these are 

 supplied by a system of water-vessels peculiar to Starfish and their 

 allies. These rays are often called " ambulacra.''^ 



In the body of the Starfish (Fig. 3) the arms are seen to be 

 continuous with the disk and to contain portions or prolongations 

 of the chief organs. The middle of the arm is occupied by two 

 rows of hard pieces (ambulacral ossicles), the fellows of which make 

 an open angle with each other, and so form an open ambulacral 

 groove ; along this we find the suckers, the water-canal that 

 supplies them, the blood-vessel of the arm, and a nerve-cord. At 



