STAR-FISH AND SEA-URCHINS. oF1 
advances with a leap or bound about the distance 
of two inches, and as the strokes follow one another 
rapidly, the Star-fish is able to travel at the rate of 
six feet per minute. A common Star-fish, on the 
other hand, with its slow crawling method of 
Fig. 46.—Natural movements of a Brittle-star when proceeding along a solid 
horizontal surface. 
progression, can only go two inches per minute. 
Some of the Comatule, in which the muscularity 
of the rays has proceeded still further, are able 
actually to swim in the water by the co-ordinated 
movements of their rays.* 
* In this case the locomotion of a Star-fish comes to be per- 
formed on the same plan or method as that of a Jelly-fish—the 
five rays performing, by their co-ordinated action, the same 
function as a swimming-bell. It is a curiously interesting fact, 
that although no two plans or mechanisms of locomotion could 
well be imagined as more fundamentally distinct than those 
which are respectively characteristic of these two groups of 
