GREGARI'NIDE. This term was applied by Leon Dufour to designate a group of microscopic organisms belonging to the sub-kingdom protozoa, which have been dis covered as parasites in the intestinal canal in various invertebrate animals, especially insects, arachnidans and certain chmtopodous worms. They seem to have been first observed by Cavolini in the last century, but the earliest systematic notice of them is that of Dufour in 1828, who gave them their name from the groups in which they occurred.
The form of the body varies: it may be cylindrical, ovate. fusiform. or threadlike.
It is often marked by indentations or strictures corresponding to the spot where an internal septum divides the organism into two or more segments. In some, a process projects from one end of the body, or there may be two lateral processes, and to these prolongations minute books are attached by which it is supposed that these animals attach themselves to the surfaces on which they are generally found. Anatomically, the gregarinidm consist of an extensible transparent membrane inclosing a granular mass, in which we observe a nucleus surrounded by a clear space. See CELLS. These organisms are colorless; their locomotive powers seem very limited; and they hay.; neither mouth nor feet.
On carefully watching them under the microscope, we observe two of them to come in contact. The surfaces in contact become flattened, and a cyst or capsule soon forms around them and Meioses them. Numerous globular vesicles are then produced in the interior, and these become ultimately metamorphosed into peculiar bodies, which are termed pseudo-naviculce. The septa= by which the two gregarinithe were at first divided; finally disappears; the cysts bursts, and the pseudo-naviculm escape, and in due time bursts also; and thus gives rise to bodies closely resembling amoeba;, minute animals belonging to the rhizopoda (q.v.), which at length develop themselves iuto young gregari
niche. The coalescence or conjugation of the gregariniche is not positively essential to the formation of pseudo-naviculaz, since they are sometimes seen to occur within the bodies of single animals.
We have followed, as we believe, the best authorities in placing the as adult forms of the group of the protozoa. There is, however, considerable difference of opinion regarding the position they ought to occupy. Stein places them among the infusoria, Leon Dufour, Leidig, Vogt, and others, place them under various divisions of the WO1'111S, while some have even held that they are vegetable forms.
It is exceedingly probable that certain minute parasitic organisms, occurring both on and within the bodies of fishes, and to which the term psorospermice has been applied, are ideutical with the pseudo-naviculm, which we have already described.
The gregarinidm have been divided into (1) the monoeystidce, when the are solitary; and (2) the Zygocystidce, when two animals are conjoined.
Numerous memoirs have been written on the gregarinidx. We may especially refer to KbHiker's memoir in the Zeitsch. f. wLssen. Zootogie (1848), and the Lieberkithn's memoir on their development in the Memoires Couronnes des Savants Strang., published by the Brussels royal academy in 1835.