THE LIVING WORLD. 
35 
With the reader’s attention thus called to the missing rounds in the ladder 
•of development up which we are gradually climbing, but with pieces of the 
broken rungs projecting barely enough for a footing, we will proceed to a 
•consideration of some of the representative types of the lower orders of. life in 
the sea, from which we will find a more perfect development in the higher 
existing classes, but in which 
there are characteristics con¬ 
necting the two plainly distin¬ 
guishable. 
The Echinoderms (or 
urchin-skinned animals ) take 
their name from the resem¬ 
blance of their spines to those 
of the hedge-hog. They glide 
along like unreal beings, owing 
to their almost unlimited num¬ 
ber of little tentacles, each ter¬ 
minating in a sucker. 
The Sea Cucumber is 
•cylindrical and has a leathery 
integument; it is an article of 
extended commerce among the 
Chinese. One species when 
not at ease will practise the sea cucumber. 
hari-kari of the Orient; but 
unlike the less skilful human being, it can reconstruct itself and renew its 
mundane existence. 
The Sea-Urchins proper have their upper portions covered by a shell, 
which is curious alike from its appear¬ 
ance, and for the mechanical skill re¬ 
quired for its construction. This shell 
is made up of a great number of curved 
plates, so that increase in size without 
loss of form can be attained by calca¬ 
reous deposit on their edges. The 
spines furnish one of the wonders of 
the microscopic world; each one is 
movable at the will of the animal, and 
has the same joining as the upper 
arm of a human being. In the meta- 
morphic period the creature is at first 
globular. It then puts forth a dome¬ 
like part, supported by frail legs, which 
leather sea-urchin (. Asthenosoma hystrix). might do honor to the slender supports 
of the furniture of a French Louis. 
It then assumes the form of a clock, with the regulation position of hands, 
which presently expand into the typical Echinoderm. 
The ordinary Star-Fish, helpless as it is in the hand of a human being, 
has been successfully rapacious beyond belief. It is specially predaceous among 
