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.

    5/16
    parent was more frequently absorbed, or at least disappeared, at other times the bond of connection remained; so that occasion- ally two, three or more larvae of different or of nearly equal size might be seen growing closely united together at the base, as if one had split itself longitudinally into two or more separate in- dividuals. This chiefly took place when the larvae were so thickly clustered together that they had not room to spread sufficiently. When the buds were developed into young larvae, these generally moved outwards from their parents to a small distance, leaving- room for those that were to succeed them. This locomotion is generally slow,—one larva that I watched moved ^ths of an inch in fourteen days,—and is effected by a sliding motion of the attached end over the substance to which it adheres. In this motion the attached end bulges outwards in the direction it is about to take (fig. 12 a), and the whole of this end gradually follows, carrying of course the whole of the upper part of the body along with it. More rarely they move more rapidly by pushing outwards a narrow prolongation similar to a long sto- lon (fig. 4 a), which becomes fixed at its further extremity, and the attached end becoming loosened, the whole body is carried onwards by the contraction of the prolonged part. The older I larvse are almost or entirely stationary. The larvae, when detached from the surface to which they are adherent, can again fix themselves. I have frequently performed this experiment by placing those detached in separate vessels, and almost always successfully, when care was taken to disturb them as little as possible for three or four days, or longer. A considerable number of larvae are adhering to the surface of the vessels in which the stones are kept *. I made several experiments upon the reparative powers of the larvae. In several the upper half of the body was cut off, and after three or four days its lower or cut end had closed in, and by the sixth day it had attached itself to the surface of the ves- sel, and shortly assumed all the appearances of an entire larva, sending out stolons and forming buds. Fig. 12 is a representa- tion of the upper half of a larva eight days after it had been cut off. New tentacula, and a new mouth also, after several days presented themselves on the upper or cut end of the lower half. Several were divided longitudinally through their entire length, and when means were not taken to keep the cut edges apart they soon adhered again, and no traces of their division remained. In one divided longitudinally the two portions were kept apart, * According to bars, “si on detache violemment ces polypes, il n’y a qu’un petit nombre qui pent se fixer de nouveau, et alors ils n’adherent pas si fortement qu’a l’ordinaire; la plupart restent fibres au fond du verre.” Opus cit. p. 339.