8 PROCEEDINGS OF THE ACADEMY OF [Jan., 



The second point concerns progression. Gregarines are stated to 

 show a " gliding " movement, and this, as we have seen, has been 

 carefully studied. But I have been unable to find m the published 

 literature on these animals any conclusive statement bearing upon 

 the question as to whether gregarines creep or swim. Gliding could 

 readily be effected in either of these two ways. When considera- 

 tion is taken of their native environment, a very strong presumption 

 is established that gregarines creep, yet certainly the matter is one 

 which necessitates a demonstration. 



This demonstration is not at all difficult. In all microscopic 

 mounts, gregarines either lie against the under surface of the cover- 

 glass or upon the slide, which can be shown by raising or lowering 

 the tube of the microscope. Either the upper or imder surface of 

 the animals remains in focus until everything else has disappeared 

 from view. This shows that all studies on progression have been 

 made on animals which are in contact with a surface. 



Gregarines possess and at times exert the power to progress con- 

 tinuously in straight lines. But more usually the progression is 

 neither straight nor continuous. The animal advances by fits and 

 starts, and the path pursued may be a zigzag or a series of curves. 

 Plate I, fig. 1 shows the positions occupied by a progressing greg- 

 arine, a being the earliest and / the latest. To the right is sketched 

 the line generated by any given point of the animal's body. 

 Under such circumstances the advance is not continuous, but slow 

 and hesitating, and accompanied by frequent stops. There may be 

 an advance of perhaps the body length, followed by a short pause. 

 Ujion progression being resumed, it may be in the same or in a 

 slightly different direction. The proper idea will be obtained by 

 supposing the stops to take place anywhere along the broken line 

 shown in the figure. 



This mode of progression is very common, and at least in Steno- 

 pohora juli is much more frequently seen than continuous progx'es- 

 sion in a straight lino. The alterations in the direction of the path 

 are not, however, always so frequent as those shown in fig. 1, and 

 the animal may advance along a series of curves. On the other 

 hand, very short turns are often seen (Plate I, figs, 2, 3 and 4). 



While progressing in any of these ways, gregarines may or may 

 not display evident muscular movements. In all published accounts 

 of gregarine progression, the statement is made that the animals 



