Nematocysts Sentence Examples
They have a number of different types of stinging cells, called nematocysts, on their tentacles.
From them are developed two distinct types of histological elements; the genital cells and the cnidoblasts or mothercells of the nematocysts.
The cnidoblasts are the mother-cells of the nematocysts, each cell producing one nematocyst in its interior.
The nematocysts of the ectoderm may be grouped to form batteries on the tentacles, umbrellar margin and oral lappets.
In places the nematocysts may be crowded so thickly as to form a tough, supporting, " chondral " tissue, resembling cartilage, chiefly developed at the margin of the umbrella and forming streaks or bars supporting the tentacles (" Tentakelspangen," peronia) or the tentaculocysts (" Gehorspangen," otoporpae).Advertisement
Jickeli (28) that the species are distinguishable by the characters of their nematocysts.
The fact already noted that the species of Hydra can be distinguished by the characters of their nematocysts is a point of great interest.
In each species, two or three kinds of nematocysts occur, some large, some small, and for specific identification the nematocysts must be studied collectively in each species.
It is quite possible that the characters of the nematocysts might afford data as useful to the systematist in this group as do the spicules of sponges, for instance.
In addition to tentacles, there may be marginal cirri (Laodice) with a solid endodermal axis, spirally coiled, very contractile, and bearing a terminal battery of nematocysts.Advertisement
They may bear accessory filaments or tentilla (f'), covered thickly with batteries of nematocysts, to which these organisms owe their great powers of -offence and defence.
Each palpacle is a tactile filament, very extensile, without accessory filaments or nematocysts.
Grosvenor these nematocysts are derived from the hydroids on which the animals feed.
Tegumentary papillae not ramified, and containing cnidosacs with nematocysts.
This aggressive character has a different aspect in several genera which are destitute of a central stylet, but in which the surface that is turned outwards upon eversion of the proboscis is largely pro- P. vided with nematocysts, sending the urticating rods of different sizes in all directions.Advertisement
To these three characters the Hydrozoa add a fourth which is distinctive of the subdivision of the Coelenterata termed the Cnidaria; that is to say, they always possess peculiar stinging organs known as nettle-cells, or nematocysts (Cnidae), each produced in a cell forming an integral part of the animal's tissues.
When the prey comes into contact with the tentacles it is paralysed, and at the same time held firmly, by the barbed threads shot out from the stinging organs or nematocysts.
The grounds for this view are the radial symmetry of several Polyclads and the supposed origin of gonads and excretory flame-cells from the walls of gut, the occurrence of nematocysts in Anonymus, one of the most radially constructed Polyclads, and lastly the presence of two peculiar animals Ctenoplana and Coeloplana, which suggests a transition from Ctenophora to Polyclads.
The distal club corresponds to the crystal-sac of an ordinary After Wladimir Schewiakoff, simplified from rhopalium, but bears a battery a coloured plate in Morphologisches Jahrbuch, of nematocysts in place of the xv., 1889, by permission of Wilhelm Engelotoliths.
By means of the stinging nettle-cells or nematocysts with which the tentacles are thickly covered, living organisms of various kinds are firmly held and at the same time paralysed or killed, and by means of longitudinal muscular fibrils formed from the cells of the ectoderm the tentacles are contracted and convey the food to the mouth.Advertisement
The lastnamed are specially numerous on the tentacles and on some other regions of the body, and produce the well-known "thread cells," or nematocysts, so characteristic of the Coe lentera.
They must first of all stop any remaining nematocysts from firing off and the best thing for this is ordinary household vinegar.
Lots of stinging nematocysts, full of venom, implant into your skin and pump in the poison.
In the middle ectoderm cell are seen a nucleus and three nematocysts, with trigger hairs projecting beyond the cuticle.
It would be particularly interesting to ascertain how the nematocysts of a polyp are related to those possessed by the medusa budded from it, and it is possible that in this manner obscure questions of relationship might be cleared up.Advertisement
The surface of the coenosteum is covered by a layer of common ectoderm, containing large nematocysts, and is perforated by pores of two kinds, gastropores and dactylopores, giving exit to gastrozoids and dactylozoids respectively, which are lodged in vertical pore-canals of wider calibre than the coenosarcal canals of the general net 'work.
The medusae of this order are characterized by the tough, rigid consistence of the umbrella, due partly to the dense nature of the mesogloea, partly to the presence of a marginal rim of chondral tissue, consisting of thickened ectoderm containing great numbers of nematocysts, and forming, as it were, a cushion-tyre supporting the edge of the umbrella.
The armour-plates are often exquisitely sculptured, and may be produced into spines or perpendicular plates to give greater surface extension, as we find in other plankton organisms. The cortical plasma may protrude pseudopodia in the longitudinal groove; it contains trichocysts in several species, true nematocysts in Polykrikos.
Jellyfish venom is delivered by barbs called nematocysts, which are located on the creature's tentacles and penetrate the skin of people who brush up against them.
Vinegar and other acidic substances are used to neutralize jellyfish nematocysts still clinging to the skin, which are then scraped off.