Observations on the minute structure of some of the higher forms of polypi : with views of a more natural arrangement of the class / by Arthur Farre.

  • Farre, Arthur, 1811-1887.
Date:
1837
Catalogue details

Licence: Public Domain Mark

Credit: Observations on the minute structure of some of the higher forms of polypi : with views of a more natural arrangement of the class / by Arthur Farre. 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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    remains suspended from the upper part of it by the intestine, which appears to have some attachment at this point. The upper part of the tube, however, is generally brought down lower than the stomach, in order that the tentacles may be completely drawn in (fig. 3. c.). By this suspension of the stomach from the upper part of the cell a fixed point is obtained, from which the retracted flexed portion of the tube may erect itself with the same effect as if the stomach were in contact with the bottom of the cell. This is a point which it would be important to observe in generic distinc- tions ; but here, as with many other points in this species, my observations were not carried to the extent that they have been in others, as this was one of the specimens with which my investigations were commenced, and I have never since had an oppor- tunity of confirming them. This is the more to be regretted, as from the complete isolation of the cells, and the extreme transparency of their parietes, a clearer view of their contents is obtained than in any species that I have subsequently met with. The spots upon the pharynx, and their absence in the triangular ciliated space, were remarkably distinct (fig. 3. a 1.), as was also the difference between the dark brown colour of the hepatic follicles in the replenished stomachs, and their pale and almost inconspicuous character in the empty ones. (Compare a and h. fig. 3.) The position of the cardia was not ascertained. When the body was turned so that the pylorus was presented to view, and this happened to be empty, a row of cilia were distinctly seen surrounding it. The vibration of these cilia, as well as of others which were observed in the stomach, appeared to be entirely under the control of the animal. Their action was frequently observed to be suddenly suspended, when the rotation of particles ceased also, and when it recommenced the motion of particles was renewed. This rotation was often so rapid at the pylorus that I should think from one to two hundred revolutions must have been performed in the minute. When very small animalcules were introduced into the bulging pharynx, several convulsive efforts were sometimes made before they could be swallowed ; during these the animalcules not unfrequently escaped again by the mouth, but were intercepted by one of the ten- tacula being bent forward and striking the animalcule as it rose with a sharp blow that drove it back again into the pharynx. The animalcules did not immediately perish in the stomach, but continued their motions for some time after being intro- duced into it. The gastric and tentacular retractors are particularly distinct, and have the usual origins and insertions (fig. 3. d 1 and 2.). The double row of parietal muscles (fig. 3. d 3.) have been already described in the notes on the species first quoted. There ap- pears to be but one set of retractors of the operculum (fig. 3. d 4.), which is generally drawn towards the side of the cell from which they arise, leaving a slight indentation in the top of the latter when retracted (fig. 3. c.). The granules on the parietes are less numerous than in most instances, but very conspicuous. The cells have an oblong form, and are connected to their narrow creeping stem by a short peduncle. The opercular portion terminates in a notched margin, and is