23G ON THE ORGANIZATION OF THE GENUS GREGARINA OF DUFOUR. 



tunic of the cephalic sac, but most commonly at some part of the sides, allowing the 

 contents to escape. 



Within the parietal tunic of the posterior sac is a second membrane, which is transpa- 

 rent, colourless, and marked by a most beautiful set of exceedingly regular, parallel, lon- 

 gitudinal lines, which in Gregarina Juli marginati measure the 1.9375th of an inch apart; 

 in G. Blatlsc orientalis the 1. 10.000th of an inch; and in G. Passali cornati the 1.15.000th 

 of an inch. This tunic has entirely escaped the notice of all previous observers, and I 

 can account for the circumstance in no other way, than by supposing it has arisen from 

 the inferiority of the microscope made by European continental artists. The lines or 

 markings are easily observed, without any other than the ordinary arrangement for light, 

 by the J of an inch, but better the T ^th of an inch focal power of the instrument of Messrs. 

 Powell & Lealand. 



Of course, if the existence of this second tunic be confirmed, and I have seen it too 

 frequently and plainly to think I have been deceived, the idea of the Gregarina being a 

 simple organic cell, is at once exploded. 



This tunic I did not detect in the cephalic sac, it appears to go only to the partition 

 dividing the latter from the posterior sac. I have considered it as a muscular or sarcodic 

 structure, because the posterior sac alone is endowed with movement, and as the parietal 

 tunic is the same in both sacs, it is reasonable to conclude the contractile power resides 

 in this second tunic. 



Situated in the granular mass of the posterior sac, is to be found one, sometimes 

 two, globular, transparent, colourless, homogeneous, elastic corpuscles, which measure 

 from the 1.4000th to the 1.275th of an inch in diameter. The elasticity of these bodies is 

 so marked, that I have occasionally observed them pressed into a cylindrical form, or con- 

 stricted into an hour-glass shape, by the contraction of the posterior cell, and upon 

 removal of pressure they would instantly resume their usual appearance. 



It is sometimes faintly granular, at other times, in its homogeneous mass may be seen 

 a few scattered, minute, transparent granules. Frequently it contains a nuclear body 

 which is globular, transparent, and homogeneous, with or without one or two nucleoli. 

 Sometimes the nucleus is coarsely granular. Occasionally the corpuscle contains several 

 nuclei. 



Movements'. Upon the endosmosis of water or saliva into the Gregarina, a quite active 

 degree of molecular movement is observable among the granules of the contents. 



The contractile movements of the animals, as before observed, take place only in the 

 posterior sac. These appear to be of a muscular character, to such a degree that I was 

 led to the detection of the muscular tunic in seeking for their source. They are slow, 

 and resemble very much the movements produced by the contractile fibres of the dartos 

 membrane of the scrotum. 



The posterior sac contracts in any part of its extent without necessarily involving any 

 other part, or it may contract simultaneously throughout. The movements consist of a 

 slow bending of any part of the posterior sac, or constriction of its parietcs, or involution 

 of any part, or contraction of the cephalic sac with involution, or general contraction re- 

 moving any involution, with projection of the cephalic cell if it had been previously retracted. 



