44 INTKODUCTION TO 7J00L0GT. 



ing fiict respecting the maternal solicitude evinced in a species 

 of Star-fish, found upon our own shores {Cribella oculata. 

 Fig. 29). The mother, by bending the arms and the lower 

 surface of the body, forms a receptacle which, in its uses, 

 may be compared to that of the marsupial animals, or to the 



pouches of the Medusre. Here 

 the ova are hatched ; and for the 

 space of eleven successive days, 

 during which this process is going 

 on, the female Star-fish has re- 

 mained in the same recurved 

 „. „„ „ „ and contracted state, and without 



Fig. 29.— Eyed Cribella. ... ^ ,. 



the possibility of taking nourish- 

 ment during that period. We do not, at present, know any 

 other example of an animal voluntarily forming a receptacle 

 for the development of its young exterior to its own body, 

 and enduring the privations consequent upon such a pro- 

 cedure. 



In this group, we find animals of extremely dissimilar 

 appearance associated together. One species is attached for 

 a certain period to a stem, and resembles a Polj'pe with its 

 waving and sensitive arms. In the common Star-fish, or 

 " five-fingers," we have the arms radiating from a common 

 centre. In the Sea-urchins, there are no arms, and the form 

 of the body is globular, and, passing over some intermediate 

 gradations of figure, we reach creatures which, in external 

 aspect, resemble worms, and have even been classed as such. 

 At one extremity of the range, the Echinodermata remind us 

 of Polypes — creatures of inferior organization; at the other 

 extremity, they approach the annulose* animals, whose struc- 

 ture is of a higher grade. Those occupymg the centre of the 

 gi-oup may be regarded, therefore, as the types or represen- 

 tatives of the class. 



In Professor Forbes' "History of the British Star-fishes, "f 

 the entire class is divided into six families. The first of these 

 includes those animals which, in a fossil state, are known as 



• A term derived from annulus, a ring, and applied to animals which 

 like the Earth-worm are composed of a succession of rings. 



f John Van Voorst: London. This is one of that beautiful series of 

 Natural History works, for wliich we are indebted to that enterprising 

 publisher. From it we have copied figures 31 and 32 ; th« latter reduced. 



