ECHINIDZ. 285 
‘content to hide themselves under the stones, while the species 
having the spines slender and the shell very thin bury themselves in 
the sand, with which they cover themselves entirely, leaving only a 
small hole to breathe through. The species of the genus Spatangus, 
which is furnished with short thick-set spines on the under side of 
its body, which spread out at their extremities like the channel of 
a spoon, proceeds with its mining operations as follows, according 
to Mr. Jonathan Franklin :—“ Figure to yourself, reader, the animal 
on the sea-shore. He commences his operations by turning the 
lower spines in such a manner as to form a hollow in the sand- 
bank, in which he sinks by his own weight; but as he sinks, a 
great number of the spines are brought into action, throwing up the 
sand with increased activity, while the sand thrown up, returning 
again, soon covers the body of the worker, and it has soon buried 
itself beneath the surface. In this situation the long hair-like spines 
situated upon the back begin to play their part; they prevent the 
sand from entirely covering the animal, by forming a little round hole, 
through which water is introduced to the mouth and respiratory 
organs.” The hiding-place of the sea-urchin is, however, easily 
detected in the sand by the hole thus arranged for the respiration 
of the animal, and the fishermen think they can predict storms 
according to the depth of the hole. 
The Echinide are reproduced by eggs, which are red and of 
almost microscopical dimensions. As it issues from the egg the larval 
form has the appearance of a very minute Infusorium. It is not at 
once converted into the perfect animal, but undergoes a certain 
metamorphosis, analogous to that of the caterpillar into the butterfly. 
But, as we have already stated in treating of the Asteride, it produces, 
at a certain stage, by some sort of internal process of germination, a 
sea-urchin, which, being at first only an organ of the larval form, begins 
to live an independent life when the nursing larval form has destroyed 
itself The manner in which the sea-urchin unfolds itself at the 
expense of the larval form is quite analogous to that which is pre- 
sented in the case of the Asterias, it is another case of alternate 
generation, of which our space does not permit us to give even a 
general outline. 
Sea-urchins are found in every sea ; they dwell in sandy bottoms, 
and sometimes upon rocky ground. They are caught with wooden 
pincers when in shallow water ; when found at the water’s edge they 
may be taken by a gloved hand. ; 
The sea-urchin, like the crab, which it also resembles in taste, 
becomes red when boiled ; only certain species are comestible, 
