A History of the British Stalk-eyed Crustacea

John Van Voorst, 1853 - 386 Seiten

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Seite xlviii - When they first escape they rarely exceed half a line in length. The body is ovoid, the dorsal shield large and inflated, on its upper edge and about the middle is a long spine, curved posteriorly and rather longer than the diameter of the body, though it varies in length in different specimens; it is hollow, and the blood may be seen circulating through it. The upper portion of the body is sapgreen, and the lower semi-transparent.
Seite xxxvi - ... muscle or tendon, the attachments of which are at each extremity. In fact, this body is perfectly defined, and can be turned out of the shell without being much injured. " When the limb is thrown off, the blood-vessels and nerve retract, thus leaving a small cavity in the new-made surface. It is from this cavity that the germ of the future leg springs, and is at first seen as a nucleated cell. A cicatrix forms over the raw surface caused by the separation, which afterwards forms a sheath for...
Seite xl - Thus, in its progress from the egg to its final development, the brachyurous crustacean was proved to pass through two temporary conditions, which had previously been regarded as types, not of genera only, but of different families ; and both strikingly dissimilar from the group to which, in its perfect state, it really belongs. " The new doctrine was not received at once with implicit assent.
Seite li - The claws undergo an entire revolution ; the first pair become stouter than the others, and are armed with a pair of nippers," the others being simple ; " but the posterior pair are branched near the base, and one of the branches ends in a bushy tuft. The tail is greatly diminished in its relative size and proportions, and is sometimes partially bent under the body, but is more commonly extended. This form is as natatory as the first. They are frequently found congregating around floating sea-weed,...
Seite l - SHOBE-CRAB, than when in confinement. Their swimming is produced by continued flexions and extensions of the tail, and by repeated beating motions of their claws ; this, together with their grotesque-looking forms, gives them a most extraordinary appearance when under examination. As the shell becomes more solid they get less active, and retire to the sand at the bottom of the vessel, to cast their shells, and acquire a new form. They are exceedingly delicate, and require great care and attention...
Seite xxxvi - A small gland ular-like body exists at this spot in each of the limbs, which supplies the germs for future legs. This body completely fills up the cavity of the shell for the extent of about half an inch in length. The microscopic structure of this glandular-like body is very peculiar, consisting of a great number of large nucleated cells, which are interspersed throughout a fibre-gelatinous mass.
Seite xlviii - ... longer than the diameter of the body, though it varies in length in different specimens ; it is hollow, and the blood may be seen circulating through it The upper portion of the body is sap-green and the lower semitransparent. The eyes are large, sessile, and situated in front, and the circumference of the pupil marked with radiating lines. The lower margin of the shield is waved, and at its posterior and lateral margin is a pair of natatory feet. The tail is extended longer than the diameter...
Seite xli - The author proceeds to examine at length the arguments on which Mr. Thompson has founded these opinions, and adduces his reasons for concluding that they are erroneous, and that no exception occurs to the general law of development in the Crustacea, namely, that they undergo no change of form sufficiently marked to warrant the application to them of the term metamorphosis.
Seite 249 - Lobsters with their young ones around them ; some of the young have been noticed as six inches long. One man noticed the old Lobster with her head .peeping from under a rock, the young ones playing around her: she appeared to rattle her claws on the approach of the fisherman, and herself and young took shelter under the rock; this rattling, no doubt, was to give the alarm.
Seite xlviii - ... life. There could be but little doubt that these creatures were the young of the captive Crabs. In order, however, to secure accuracy of result, one of the Crabs was removed to another vessel, and supplied with filtered water, that all insects might be removed ; but in about an hour the same creatures were observed swimming about as before. To render the matter, if possible, still more certain, some of the ova were opened, and the...

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