MANUAL OF NATUKAL HISTOEY. 321 



bestowed upon the members of this Sub-kingdom ; 

 their powers of locomotion are also limited, and 

 their muscles weak and rudimentary. In the higher 

 forms the digestive organs are well developed; the 

 circulation is carried on in distinct blood-vessels, 

 although the heart is wanting; and the mode of 

 reproduction is by fertile ova, but without the mu- 

 tual co-operation of the sexes. 



Foremost in the rank of animals constructed on 

 the radiate type, stand the hard and rough-skinned 

 Echinoderms, locomotive stomachs, groping their 

 way, mouth . downwards, along the bottom of the 

 sea, true " scavengers of the deep " singular beings, 

 varying extremely in their outward form ; sometimes 

 soft and languid like the worm-like Holothuria and 

 the mud-boring Sipunculus ; sometimes with fixed 

 calcareous stems, and jointed tentacle-like rays, as in 

 the zoophytic Encrinite, or detached and free with 

 compound plumose arms, like the elegant Antedon ; 

 or sometimes snake-rayed, like the Ophiurus ; mem- 

 branaceous, like the Palmipes ; flattened and shield- 

 shaped, like the Clypeaster ; ovoid, like the Spatan- 

 gus ; or spinose and globular, like the Echinus and 

 the Cidaris. 



Here also we place the Acalephce, elegant pellucid 

 beings, symmetrical and of delicate organization, 

 and yet the sport of oceanic waves ; whose skin, 

 though not of leathery toughness or bony consist- 

 ence, yet possesses the remarkable power of para- 

 lyzing their prey, and producing a stinging sen- 

 sation when handled. Like the Star-fishes and 



p 5 



