ON THE ORGANIZATION OF THE GENUS GREGARINA OF DUFOUR. Ji."> 



The Gregarina is a very simple form of cntozoon infesting insecta, Crustacea, myria- 

 poda, and annelida. In insecta and myriapoda I have usually found them within the 

 proven triculus, but occasionally within the cavity of the abdomen applied to the exterior 

 parietea of the organ just mentioned. They are usually more or less wrinkled or flaccid, 

 ept in the full-grown condition, when they arc more or less distended with the granular 

 contents. 



When the gastric fluid in which the parasite is found is diluted with water, it becomes 

 distended by rapid endosmosis, and soon undergoes destruction. The fluid which I used 

 in examining them, and which I generally use in investigating the delicate tissues of in- 

 sects, is the blood of the latter. The Gregarinse are not always loose and floating, but 

 are frequently found attached by the posterior end to the delicate transparent epithelial 

 layer, which is so often seen detached in the form of a cylinder from the interior parietes 

 of the proventriculus of insects, and when the animals are separated they may often be 

 observed with a shred of membrane attached, as represented in fig. 3, pi. 10. 



A Gregarina consists of two portions or divisions of the body, which, for convenience, 

 I will call the cephalic and posterior sac, the former of which is considerably smaller in 

 size than the latter, and is placed anteriorly upon it, or partly in a depression in it, and both 

 are intimately connected together by the tegumentary tunic. 



Each sac contains within the interior a mass of granular matter, which, according to 

 the quantity, will appear whitish and translucent, or white and more or less opaque, 

 although the constituent granules of the masses are transparent, resembling oil granules, 

 and measure from a mere point to about the 1.7500th of an inch. The granules arc 

 smaller and fainter in the young animals, and in the oldest individuals they exist to such 

 an extent as to give them a milk-white opaque appearance. Frequently there arc some 

 granules of a larger size than ordinary mixed with the others, but still preserving the same 

 structure. 



Tincture of iodine renders the masses of granular matter brown; ether causes many 

 of the granules to run together and form large globules. 



The granules of the masses are held together by a clear, colourless, viscid, albuminoid 

 fluid, which is coloured brown by iodine, and faintly yellow by nitric acid and ammonia. 



The parietal tunic of the sacs is colourless, transparent, and structureless, or amorphous 

 in structure. A partition of the same character passes between the two sacs, separating 

 the granular masses from each other. 



This tunic is softened or even dissolves in acetic acid; iodine turns it brown; nitric 

 acid and ammonia faintly yellow. 



It completely closes the posterior sac from all communication with the exterior and 

 also from the interior of the cephalic sac. 



It forms the cephalic sac, which appears also to be closed from the exterior. At the an- 

 terior part of this sac it is frequently thickened into a papillary eminence, and sometimes 

 »a pi 1 into a proboscidiform appendage. 1 could never ascertain beyond all doubl 



whether there was not a communication from the interior with the exterior, through this 

 ■ interior thickening of the tegument. When the animal is submitted to pressure, both 

 may be burst, rarely one into the other, or through the papillary thickening of the 



