THE ANBrAL LIFE OF THE GROUP. 489 



to connect with the bulb-like sacks i" tluit in tuni connect with the tube-feet. 

 Sea water is forced into this system of tubes and by the expansion ov contrac- 

 tion of the little sacks, the feet are thus extended or withdrawn. 



The favorite food of the starfishes is said to consist of the connnon bivalves, 

 but it is asserted that there is no animal that it can catch that it will not 

 devour. On the oyster beds, especially along the Atlantic coast, they are vei-y 

 destructive. They wrap themselves about the oyster and in so doing- literally 

 turn the stomach inside out through the mouth. In a little while the bivalve is 

 forced to relax its muscles and allow the shell to oi)en. The edge of the 

 stomach is then inserted between the valves of the shell and the soft parts of 

 its prey are thus digested outside the starfish's body. The habits of our Ha- 

 waiian species have not as yet been studied, though it would not be a difficult 

 matter to do so. 



Large specimens of an eight-rayed starfish ^^ are occasionally captured ;it 

 Pearl Harbor. They are often a foot and a half in diameter, are cream-colored 

 above, mottled with burnt sienna and chocolate, and are white below. A 

 similar but very small species is to be found abundantly in the coarse green 

 sponges in Kalihi bay and at Pearl Harbor. A small, stiff, irregularly-de- 

 veloped pink leather-like species,!^ without spines, is occasionally found 

 crowded into small holes in the coral reef. It is remarkable for its powers of 

 reproducing new and complete animals from the broken fragments of the old 

 one; a single specimen in the laboratory has been made to produce a dozen or 

 more complete animals from the fragments broken from the pareni, while the 

 parent disk has gone on and reproduced all the lost parts. 



A c\u"ious five-sided form, ten inches or more in diameter, has also been 

 taken in the shallow water in Pearl Harbor, but of recent years the dredging 

 operations have apparently driven the large species away. My friend Dr. 

 Walter K. Fisher was on the great Albatross expedition and has described 

 fifty-two of the sixty species taken on that cruise as new to science. They are 

 placed in twenty families and are distributed into no fewer than forty-six genera. 

 As can be imagined, the collection represents a inost astonishing variety of 

 starfish forms. But as the collection was niiulc in w.-itei- fi-om Icn to a thou- 

 sand fathoms down, his splendidly-illustrated monogra])h is an iiidrx to what 

 is in the great deep oft'shore, rather tlian a guide to the forms liahlc to be 

 gathered by hand by the wading naTiiralist. 



The Brittle-St.vrpish. 



The brittle-stars 1*' have long serpent-like arms attarhed to a i-clati\el\' 

 small and usually rounded disk-shaped body. They differ from the true stars 

 in a number of ways. It is important to note that the digestive system does 

 not extend into the arms, but is confined in the centi-al body, and that they 

 have no grooves on the under sidi' of the arms, such as exist in the typical star- 

 fish. The arms are long and very (Icxihlc and ai-e used almost entirely as the 

 organs of locomotion. 



13 Ampulla;. '* Liiidia In/xtrix. ^'' Liitckia sp. '" Oiihi>in,i,l,n. 



32 



