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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    observed the slightest traces of the hollow quadrangular body described by Steenstrup as growing from the lower surface of the cavity or stomach in the body ot the animal, sometimes pro- jecting as high as the mouth, and placed in the middle of the stomach, like the clapper in a bell. The inner surface of the lips and of the stomach, and the ex- ternal surface of the tentacula and body, are covei’ed with very fine cilia, so that currents of water, unless when the mouth is shut, are constantly passing in and out from the mouth and along the tentacula. The cilia upon the external surface of the body re- quire the use of the higher object-glasses for their detection, and for a long time they escaped my notice. The colony of larvae first obtained began to produce buds and stolons about the middle of January 1846, and the other two colo- nies at the end of July of the same year. With intervals of com- parative repose they have gone on reproducing abundantly ever since; so that, notwithstanding they are constantly suffering loss by death and other causes, the number of individuals in each colony has greatly increased. Whenever buds and stolons are formed, they commence by a thickening of the internal layer at those parts, causing a bulging outwards of the external layer. A single bud (fig. 10 a), occasionally two buds, grow from the upper surface of the stolon, and these become developed into larvae in the manner described by Sars. The buds form upon all parts of the external surface, but most frequently near the lower part, of the body. On many of the larger larvae several buds were seen growing at the same time (fig. 11a). As a bud enlarges it becomes elongated and attenuated at its free extre- mity, and bends itself downwards to reach the surface of the stone to which the elongated extremity adheres: after this the attached end is gradually separated from the body of the parent. When thus detached, a small opening presents itself at its upper end, its interior gradually becomes hollowed out and cilia grow upon it, and tentacula commence to sprout around the mouth, exactly in the same manner as in the buds formed on the upper surface of the stolons. The outer surface of the buds is also covered with very fine cilia. Several of the buds were found lying loose at the bottom of the vessels in which the stones are kept, probably detached by accident, and these after a time fixed themselves to the surface of the vessels, and passed through their development into larvae in the same manner as those that adhered for a longer time to the bodies of their parents. One of these detached buds fixed itself at two separate points, and two mouths, each furnished with its own tentacula, were formed at opposite ends of its upper surface. When a bud was deve- loped on a stolon, the connecting part between the bud and the i 1 I (I l < i,