12 PROCEEDINGS OF THE ACADEMY OP [Jan , 



sing gregariue, and constituting a trail behind it. I made this 

 observation but once, the gregarine being Echinomera hispida. 

 AVith Stenophora juli I have never been able to see it. My observa- 

 tion differs from those of Schewiakoff in that the trail does not 

 consist of fibres, but of a series of splashes (Plate II, fig. 8). The 

 substance arose from the surface of the gregarine as short rods, 

 which almost instanty expanded into irregular drops. These drops 

 then became detached from the surface of the gregarine to con- 

 stitute the trail. 



I do not think that this observation gives any I'eason for ques- 

 tioning Schewiakoff ' s statement that the gelatinous substance passes 

 backward as fibres. But since an extrusion of the sort shown in 

 fig. 8 could hardly push the animal forward, the observation appears 

 to me significant in indicating that the trail is the effect of progres- 

 sion and not its cause. It is an intrinsic weakness of Schewiakoff ' s 

 explanation that it gives no reason why the gelatinous substance 

 should pass backward instead of either forward or radially. If, 

 however, the cause for progression is to be sought for elsewhere, it 

 is easy to see why it passes backward. Upon its emergence on the 

 surface of the gregarine, it is merely left behind, in precisely the 

 same way as the mucus secreted by a snail is left behind as the 

 animal advances. The passing backward of the gelatinous substance 

 is the effect of progression, and not its cause. 



As Schewiakoff states, progressing gregarines gather up and drag 

 behind them masses of loose particles. The size of these masses is 

 shown in figs. 9, 10 and 11. It often happens, however, that a 

 gregarine may travel for a considerable distance without gathering 

 up any such appendage. Except for perhaps half a dozen carmine 

 particles x>v minute fat-drops, the animal drags nothing along behind 

 it. This suggests that the quantity of adhesive substance on the 

 surface of gregarines is subject to variation. 



Whether Schewiakoff believes that the ability to extrude a gela- 

 tinoas substance has been developed in gregarines for the purpose 

 of locomotion does not appear. The extrusion of slimy substances 

 by endo-parasites is, however, a common phenomenon, and we 

 should look to find this power in a gregarine, just as we find it in 

 a cestode. 



In some cases, however, the sticky substance on the surface of 

 gregarines appears to be derived from the host-tissue. To study 



