" GROUSE DISEASE " STRONGYLOSIS 



227 



the worm requires to exert itself to a much greater extent in The first 

 order to entrap small solid particles of food into its rigid mouth ^dysis r 

 capsule. If, however, the culture is of such consistency that 

 the embryo is able, by burrowing its way through the faecal 

 matter, to force this into its mouth capsule, there follows a 

 very rapid growth in size 

 even when there is a marked 

 lack of oxygen. Under 

 these favourable conditions 

 of food supply an embryo 

 increases in size to such an 

 extent that on the fourth 

 or fifth day from the com- 

 mencement of the culture 

 it is obliged to shed its cuti- 

 cular covering. At this time 

 thousands of very delicate 

 sheaths may be found float-, 

 ing in the culture for a few 

 hours ; but they very rapidly 

 disappear. 



No important structural 

 alterations accompany this 

 first moult or ecdysis, but 

 during the succeeding three 

 or four days certain changes 

 within the body of the worm 

 gradually become evident. 



The cylindrical mouth 

 capsule (Fig. 28) slowly loses its 

 clear cut border and appears to be undergoing absorption, and its The meta- 

 lumen decreases (Fig. 29). At the same time the oesophagus mor P hosis 

 lengthens, the bulbous posterior portion becomes pyriform, and 

 later merges into the anterior portion, but so gradually as to 

 be only definable with difficulty. The cuticular lining of the 

 whole oesophagus, and the marked triradiate lining of the 



FIGS. 26 AND 27! 

 Newly hatched embryos of T. 

 pergracilis, highly magnified. 



