Descriptions of three Filariae / by Joseph Leidy.

  • Leidy, Joseph, 1823-1891.
Date:
1850
Catalogue details

Licence: Public Domain Mark

Credit: Descriptions of three Filariae / by Joseph Leidy. 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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    of a viscid character, for if any of these cells of the arms of the Hydra come in contact with its own body, they adhere with such tenacity, that the former can only be detached, at the expense of the loss of several of the nettling cells. From the detached cells often being found attached to the Hydra itself by the long threads, some observers, as Ehrenberg,* have considered that they were organs, which the animal ihrew out from itself like anchors. The second form of nettling organs, are found arranged in more or less regular circles around the first or largest form, usually nine to fourteen in a circle. They are transparent, pyriform, about l-3400th in. in length by ]-5666th in. in breadth, and have projecting from the prominent extremity a cilium about l-875th in. in length. These cells are described by Corda as containing a thick walled sac, adhering to the outer cell at the base of the cilium. According to my obser- vations, the appearance of an inner sac arises from a contained thread which forms a double spiral, one end of which forms the cilium projecting from the nettling cell. The third form of nettling organs, are found in greatest abundance about the head of the animal, but also exist upon the arms, particularly at the lower part, and upon the surface of the body generally. This form appears never to have been before noticed. They are oblong, transparent cells, about 1-2125th in. long by l-5666th in. broad, and contain within them a spiral thread, more delicate than in the second form of cells, and have a greater number of turns which take a direction transversely to the length of the cell. They resemble very much in their appearance one of the forms of nettling cells of Corynactis, figured by All- man in the 17th vol. of the Annals of Natural History, PI. 11,fig.4. I have never been able to see the threads prolonged externally, on account of their minuteness, in contact with the prey of the Hydra ; but by pressure and the continued en- dosmosis of water I have detected them protruded in this as well as the second form described. All the forms of nettling organs are placed within especial organic cells, adher- ing by the more prominent extremity of the organ to that part of the interior pa- rietes of the cell, corresponding to the free surface of the animal upon which they are placed. Their developement is special from the granular contents of the or- ganic cells and not from the nucleus, for in the first or largest form of nettling organs, in their developement upon a bud of the Hydra, I have been able to detect one within an organic cell, and a nucleolated nucleus at its side. The foregoing observations have been made in frequent efforts to detect some fo rm of cell within the head of the Hydra which would be different from the gene- ral structure ofthe body, and probably characterize a nervous system, but although I have examined the animal in different menstrua under a variety of circum- stances, I have never been able to discover anything whish could be referred to a T -vous structure. • Not. Act. Phys. Med. 1836, p. 301.