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THE AUSTRALIAN MUSEUM MAGAZINE. 



Mosaic starfish (Plectaster decanus). 



Usually an inhabitant of deep water, but not uncommonly found on 

 rock faces in sheltered water below the limit of the low tide. In life 

 this is an extremely brilliant object, the upper surface consisting of 

 red patches ornaments 1 with a network of white calcareous ridges. 



Photo. — A. Miissi'avc. 



digestive organs of 

 the original animal 

 and takes them for 

 its own use, though 

 it grows a separate 

 mouth of its own. 

 The poor foster- 

 mother (lies and ac- 

 tually becomes part 

 of the food of the 

 new animal, whicfi 

 has grown from a 

 part of the foster- 

 parent's body. The 

 sea-urchin, which is 

 also a close cousia 

 of the starfish, has 

 a development some- 

 what similar. 



BRITTLE-STARS. 



quently attacks a morsel far larger than 

 its own mouth (which is in the middh' 

 of the underside of the central disc.) 

 This does not distress the starfish, be- 

 cause it can perform a most extraordin- 

 ary feat with its inside. When it can- 

 not get its food to its stomach, it does 

 the opposite, and takes its stomach to 

 the food. It projects its stomach out 

 through its mouth, folds it around the 

 victim, and keeps it there until all the 

 food is digested. When that is done 

 the stomach is drawn ba,ck again to its 

 proper place. The walls of the stomach 

 are very loose and crinkled inside tlip 

 l)ody, and this allows for the necessary 

 stretching. 



The starfish has the property of ab- 

 solute indifference to mutilation. If 

 divided into halves each half grows an- 

 other, and we have two animals instead 

 of one. 



The life history of the starfish is also 

 very extraordinary. It comes from an 

 egg which gives forth a tiny free-swimm- 

 ing creature something like a micro- 

 scopic worm. This animal grows and 

 grows, but it is not the future starfish. 

 For, after a time, from a small rudiment 

 inside it another animal grows, and as 

 it progresses it steals the stomach and 



Very curious are 

 the brittle-staxs,. 



common on the rocky 

 shores at low tide. 

 Like a starfish in appearance, they are 

 quite unlike it in movement, for their 

 arms are long and very flexible, and, 

 unlike the starfish, which creeps slowly 



The eight-rayed starfish (Asterina calcar), 

 and the five-rayed starfish (Asterina exigua), 

 are our two commonest forms, and, occur 

 abundantly in pools left by the receding tide. 

 Photo. — A. ilusKrave. 



