94 ECHINODERMATA. 



The Asterias (/lacin/is is provided with long rays, which issue 

 from the parts around the mouth, for there is no definite central disc, 

 l^roperl}' so called, whence they could originate, although the body 

 is thick and compact. The back is somewhat elevated ; the under sur- 

 face flattened, with the dilatable mouth in the middle. Thus, there 

 being no central body, as in the Ophiura, the rays may be said rather 

 to fork from each other than to issue from a centre. These are stout 

 and taper, convex above and flattened beneath, terminating by several 

 slender suckers at the extremity, besides which there is a channel in the 

 under surface, with rows of suckers, more numerous, stronger, and of 

 larger dimensions, serving as feet, both in progression and for fixture. 



The Northern Sea-star is among the largest, the most powerful, and 

 ravenous of its kind, expanding completely twelve inches between the 

 tips of the opposite rays. But, the actual dimensions, and the wonted 

 appearance of such animals, are much affected by temperature of the 

 atmosphere, repletion with food, and especially by the presence of spawn. 



The colour is extremely variable, dependent on the specimen, and 

 sometimes on age. It is usually pui'ple or greyish : in an early state it 

 is white. I have seen cream-coloured specimens expanding towards 

 three inches. 



The richest purple adorns some specimens. Purple seems the natural 

 colour of the species. A specimen, so pale as to be almost white, having 

 been committed to recent sea-water, became speedily of a purple hue. 



^Vhen inactive, the animal is greatly contracted, crouching closely 

 in some cavity, as if for concealment, or occupying an angle, apparently 

 quite helpless and incapable of resistance. When roused by heat or 

 hunger, it advances as if half-swimming, with iiicredible quickness, such 

 as could not be ascribed to its nature without ocular demonstration. 

 The body is much relaxed, the rays extended, and the numerous suckers 

 in action. It never swims, however, nor does it spontaneously quit the 

 water, though seen as left behind by recess of the tide. 



No creature is more rapacious. Its prey is devoured aUve, whenever 

 it can be overpowered. Let a moderate-sized mussel be presented, it is 

 straightway covered by the body of the Star- fish, while the rays closing 

 around it, the animal sustains itself on them as on feet, contracting still 



