"GKOUSE DISEASE" STRONGYLOSIS 



225 



clearly defined, and now appear as cylindrical turgid cells distended with large 

 globules of highly refractile substance, giving the larva a characteristic appear- 

 ance by which it can be readily distinguished from free-living nematodes 

 (Fig. 26). 



The whole body appears to have slightly narrowed during the process of 

 metamorphosis, by the conclusion of which the larva has become changed into a 

 slender actively moving worm, with a simple elongated oesophagus without mouth 

 capsule (Figs. 26, 28). Accompanying the metamorphosis in structure is a marked 

 change in habits, for instead of burrowing into the denser portions of the food 



FIG. 24. 



FIG. 27. 



FIG. 25. FIG. 26. 



Changes in T. pergracilis during ecdysis and encystment. 



these metamorphosed forms now rush about with great rapidity, and either wriggle 

 into the patches of open water or make their way on to the actual surface of 

 the culture, and may be seen standing out in numbers into the moist atmosphere 

 above, forming a kind of hoar frost on the surface of the faeces apparently in 

 search of oxygen. Those larvae, which are fortunate enough to be near the edge 

 of the culture, ascend in the condensed water on the sides of the Petri dish and 



make their way on to the upper part, eventually reaching the blotting paper. 

 VOL. i. p 



