. Jelly-fish, star-fish and sea-urchins [microform] : being a research on primitive nervous systems. Nervous system; Jellyfishes; Starfishes; Sea urchins; Nerveux, Système; Méduses; Astérides; Echinides. 1 <'' i! :i •-vi 266 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. closely resembles sea-water, but is, nevertheless, richly corpusculated; it coagulates when exposed to the air, and otherwise shows that it is something more than mere sea-water. If we look closely into the shell which has been deprived of its spines, we find that it is composed of a great number of small hexagonal plates (Fig. 41
. Jelly-fish, star-fish and sea-urchins [microform] : being a research on primitive nervous systems. Nervous system; Jellyfishes; Starfishes; Sea urchins; Nerveux, Système; Méduses; Astérides; Echinides. 1 <'' i! :i •-vi 266 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. closely resembles sea-water, but is, nevertheless, richly corpusculated; it coagulates when exposed to the air, and otherwise shows that it is something more than mere sea-water. If we look closely into the shell which has been deprived of its spines, we find that it is composed of a great number of small hexagonal plates (Fig. 41), the edges of which fit so closely together that the whole shell is converted into a box, which, when the animal is alive, is water-tight, as we have proved by submitting the contained fluid to hydrostatic pressure, under which. li', ii Fig. 41.—A portion of the external shell of an Echinus denuded of spines and slightly magnified, showing the arrangement of the plates, the balls in the ball- and-socket joints of the spines, and the holes through which the ambulacral feet arc prptruded. (From CasscU's "Nat. ;) circumstances there is no leakage until the pressure is sufiicient to burst the shell. Nevertheless, if we look closely at the dried shell of an Echinus, we shall see that it is not an absolutely closed box; for we shall see that the hexagonal plates are so arranged as to give rise to five double rows of holes or pores (Fig. 41), which extend symmetrically from pole to pole of the animal (Fig. 39). It is through these holes that the tube-feet are protruded; so that if we imagine a pentagonal species of Star-fish to be curved into the shape of a hollow spheroid, and then converted into a calcareous box with holes f# [ m. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Romanes, G
Size: 2137px × 1169px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdeca, booksubjectnervoussystem, bookyear1895
