Observations on the development of the medusæ / by John Reid.

  • Reid, John, 1809-1849.
Date:
[1848]
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the development of the medusæ / by John Reid. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    and in eacli the cut edges approximated and adhered, and two separate animals were thus produced from one. The larvae are voracious, and readily seize and swallow uni- valve or bivalve molluscans, or a crustacean, as large or even larger than their own bodies before they are stretched out, and after retaining them in the stomach, generally for about twenty- four hours in summer and nearly twice as long in winter, they reject them through the mouth. They also not unfrequently swallow one of their neighbours, and its sojourn in the stomach for some time terminates in its digestion and destruction. When they seize a univalve molluscan too large to be swallowed, they retain it firmly embraced in their tentacula, and insert their elon- gated mouth into the interior of the shell; and in like manner they keep dead articulate animals, or molluscans without shells, too large to be swallowed, in their tentacula for more than a day, and probably extract nourishment from them by acting on their textures by their extensible lips. The larvae of the first colony, obtained in September 1845, did not split transversely into young Medusae in the spring of 1846, as I expected them to do, but continued to produce stolons and buds abundantly. A great number of them had then attained a large size, and many of them presented on their outer surface transverse rug: .ad four pretty deep equidistant vertical grooves, as repre- sented in fig. 13, but none of them presented the appearances now about to be described, indicative of their splitting transversely into young Medusae. In the beginning of February of the present year, the upper part of the body of some of the larvae of the first colony became cylindrical, considerably elongated and much diminished in diameter, with thickly-set rings forming at the top. From the circumference of the rings first formed eight equidistant lobes or rays began to grow, the rings increased in size and became of a reddish brown colour, the tentacula gradually wasted away, and in the course of eight days the young Medusae were beginning to detach themselves in the manner described by Sars. W hile this was going on at the upper part of the body, the process of elon- gation and the formation of new rings was proceeding downwards, as represented in PI. VI. fig. 14, so that thirty or forty rings, each of which was about to become a young Medusa, could be counted on the body of one larva at the same time, and the body in some cases measured three-fourths of an inch in length. At this period the upper part of the body was of the form of an in- verted pyramid, and had a distinctly reddish brown colour. As the grooves separating the rings increased in depth, it was ob- served that the body of the young Medusa above was at last attached only to the upper margin of the lips of the one below. Fig. 15 is a greatly enlarged representation of one of these young