Hardwicke's science-gossip : an illustrated medium of interchange and gossip for students and lovers of nature . ch it clings to the smooth surface of the glass or stones. Eachof these suckers is terminated by a disc, the skele-ton of which presents the same calcareous networkas the shell, but in a more beautiful and symmetricalform. Eig. 62 gives a magnified representation ofthis ambulacral disc, as it is called. In many foreign species of Echinus the spines,when examined in section under the microscope,present a very beautiful appearance, somewhatsimilar to that of exogenous wood. This appea
Hardwicke's science-gossip : an illustrated medium of interchange and gossip for students and lovers of nature . ch it clings to the smooth surface of the glass or stones. Eachof these suckers is terminated by a disc, the skele-ton of which presents the same calcareous networkas the shell, but in a more beautiful and symmetricalform. Eig. 62 gives a magnified representation ofthis ambulacral disc, as it is called. In many foreign species of Echinus the spines,when examined in section under the microscope,present a very beautiful appearance, somewhatsimilar to that of exogenous wood. This appear-ance is produced by successive rings of open spacesand solid pillars, which mark the yearly growth ofthe spine. Although the spine of Echinus lividus does notpresent this beautiful ringed appearance, doubtless,as has been suggested, from its being the result ofonly one years growth (being exuriated and repro-duced annually), still it presents a very strikingappearance. It is, in common with the species ofother echini, composed of solid calcareous ribs,alternating with bands of an open calcareous Fig. 63. Transverse Section of Spine, x 60. These ribs and bands in section appear as alter-nating rays, and the network being coloured purple,they are very striking. Eig. 03 represents a trans-verse section of the spine, and exhibits the alter-nating bauds of solid ribs and open network. Attached by a peduncle to the spines are tobe found the curious bodies called , at one time supposed to be parasites, arenow generally considered as simple appendages tothe spine, although their function is somewhatdoubtful. Each of these consists of a thin cal-careous stalk, surmounted by a curious pincer-likeapparatus, the whole being invested by the generalanimal membrane of the Echinus. Eig. 6± representsthe head of a pedicellaria. The pincers are double,and are formed of a fine calcareous network, resem-bling that of the shell. The edges of each limb ofthe pincers
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectscience
