^0 Gerald F. Hill : 



inuscae within tlie interiuediary, also (xciir in a closely similar 

 manner in H. niegastonia and in H. microstoma. 



It is worth recalling here that 1 have been jible to show that 

 .several steps in the development of H. muscae occur in the fly- 

 larvae and pupae of Musca domestica before the stage in the fly- 

 pupae which Kansom has designated Stage 1, but for the con- 

 venience of other workers, T have adhered to the designations 

 adopted by Ransom, in spite of the ciiticisms made by Seurat. 



In each case, the " fifth stage " is that in which tfie spinous 

 •character of the tip of the tail is first seen, viz. : — beneath the 

 cuticle, the anal operculum being still present, and the anus closed. 

 The "sixth stage" is charactei-ised by the further development of 

 the spinous tip of the tail, by the disappearance of the anal oper- 

 <;ulum and the opening of the anus. 



In the preceding text it has been stat-f.-d that it is possible to 

 "differentiate between H. megastoma on the one hand and H. muscae 

 ^nd H. microstoma on the other in the later larval stages reached 

 in the body of the fly, for the characteristic appearance of the 

 head of the adult H. megastoma can be detected in the fourth larval 

 stage of this worm as found in the adult Musca domestica. Fur- 

 ther, comparative measurements have been given to support the con- 

 clusion that it is possible also to differentiate between larval H. 

 muscae and H. microstoma in at least the sixth or final stage. In 

 view of the importance attached to the correct specific diagnosis of 

 the parasites found in, and supposed to be the causative agents of, 

 the lesions known here as '* Habronemic conjunctivitis," and " Hab- 

 ronemic granulomata," and also to enable others to more correctly 

 identify larvae belonging to any one of these three species found in 

 •caught flies of the same and other host species, it appears desirable 

 to discuss further one aspect of the evidence on which the writer 

 has based his statements and conclusions, namely, the evidence con- 

 tained in Tables 1, 2, 3, and 4 of this Report. For this purpose 

 the length of the body and the distance of the pharynx, nerve-ring 

 and oesophagus respectively from the anterior end of the body will 

 be considered. In Table I (H. muscae from "clean " adult Mnsca 

 domestica). Specimens 1-6, all of which are in the sixth or final 

 stage attained in the body of the fly, show the length of the body 

 to be from 2.310 mm. -2. 541 mm., an average length of 2.398 

 mm. The length of the oesophagus is from 0.83 mm. -0.97 mm., or an 

 average length of 0.898 mm. The distance of the nerve-ring from 

 the anterior end of the body is from 0.132 mm. -0.14 mm., an 



