STAR-FISHES. 
101 
commonest of objects on every shore, is an excellent 
example of this order. 
Now here we have a very evident tendency to centra- 
lisation. There are five distinct radiating arms, as in the 
Brittle-star ; but they are massive, thick, short, and com- 
paratively inflexible, while the disk or central undivided 
portion bears a much greater proportion to the whole 
expanse. 
But a change much more remarkable has been effected 
in the manner of progression. Jn the Feather-star, as we 
have seen, the motion is truly natatoi'y, performed by the 
alternate contraction and expansion of its inflated arms, 
aided, perhaps, by the lateral pinnse, with which these are 
furnished. In the Sand-stars and Brittle-stars the swim- 
ming faculty is lost ; the animal drags itself over the 
stones and even up perpendicular surfaces by its flexible 
arms, the spines of which catch hold of every projection 
and roughness. In the Star-fishes a new set of organs is 
developed, highly curious in their nature, and, like all 
other of the works of God, well qualified for their 
office. 
Let us go to the first Five-finger we see lying on the 
shingle, and turn it over. We now see that each of the 
five rays has a deep furrow running along its under sur- 
face, proceeding from the mouth in the centre of the disk, 
even to the tip of the arm. This furrow has been fanci- 
fully named tho ambulacrum , or avenue. 
Now let us, in the plentitude of our compassion, take 
the poor wretch from the stones where he lies broiling in 
the burning sun, and, bearing him home, gently place him 
in a glass vessel of cool sea-water. Our virtue will be its 
