. Animate creation : popular edition of "Our living world" : a natural history. Zoology; Zoology. THE COMMOX SEA-URCHIX. 545 The shell is composed of a vast number of seixirate pieces, whose junction is evident when the interior of the shell is examined, but is almost entirely hidden by the projec- tions upon the outer surface. These pieces are of a hexagonal or pentagonal shape, with a slight curve, and having mostly two oi)i)osite sides much longer than the others. As the animal grows, fresh deposits of chalky matter are made upon the edges of eacli plate, so that the plates increa
. Animate creation : popular edition of "Our living world" : a natural history. Zoology; Zoology. THE COMMOX SEA-URCHIX. 545 The shell is composed of a vast number of seixirate pieces, whose junction is evident when the interior of the shell is examined, but is almost entirely hidden by the projec- tions upon the outer surface. These pieces are of a hexagonal or pentagonal shape, with a slight curve, and having mostly two oi)i)osite sides much longer than the others. As the animal grows, fresh deposits of chalky matter are made upon the edges of eacli plate, so that the plates increase regularly in size, still keeping their shape, and in consequence the dimen- sions of the whole shell increase, while the globular shape is preserved. If a fresh and perfect specimen be examined, the surface is seen to be covered with short sharp spines set so thicldy that the substance of the shell can hardly be seen through them. The structure of these spines is very remarkable, and under tlie microscope they present some most interesting details. Moreover, each spine is movable at the will of the owner, and works upon a true ball- and-socket joint, the ball being a round globular projection on the sur- face of the shell, and the socket sunk into the base of the spine. When the creature is dead and dried, the membrane which binds to- gether the ball-and-socket joint be- comes very fragile, so that at a slight touch the membrane is broken and the spines fall off. Other i)eculiarities of structure will be noted in connection with the different species. The common Sea-urchin is edible, and in some places is extensively consumed, fully earning its title of Sea-egg, by being boiled and eaten in the same manner as the eggs of poultry. The fishing for these creatiires in the Bay of Naples is graijhically and quaintly described by Mr. R. Jones:— '' I had not swum very far from the beach before I found myself sur- rounded by some fifty or sixty human heads, the bodies belonging to
Size: 1164px × 2147px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorbr, bookcentury1800, bookdecade1890, booksubjectzoology
