Insedis and Parasitic Diseases. 2'S 



was surrounded by a somewhat clear space extending nearly to the 

 body Avail. Its total length was 0.3 mm. the oes-ophagus was 0.117 

 mm. from the anterior end, and the diameter at the anterior 

 margin of the rectum was 0.054 mm. 



On the same date another larva of similar appearance, measur- 

 ing 0.27 mm. in lengtli, 0.05 mm. in width near the rectum, and 

 having an oesophagus 0.11 mm. long, was found in a pupa from 

 the same culture- 



The larva shown in Fig. 7 is in the same stage of development 

 as that sliown in Fig. 6. It measured 0.34 mm. in length, 0.04 

 mm. in width at about the posterior end of the oesophagus, 0.05 

 mm. in width near the rectum, and 0.04 mm. from the anus to the 

 tip of the tail. There Avas a constriction in the intestine near the 

 junction with the oesophagus, but in living specimens this was seen 

 to be due to the movements of the intestine itself. That the 

 process of moulting had commenced Avas shoAvn by the presence of 

 the old cuticular lining of the oral cavity becoming detaclied from 

 the body. 



Fig. 8 agrees Avith the stage figured and described by Ransom 

 1913, p. 17, under the designation Stage 1, i.e., the earliest stage 

 of H. muscae definitely knoAvn to him to occur in Musca domestica. 

 The parasite shoAvn in Fig. 8 Avas found on December 6th in a fly 

 pupa, resulting from a larva AAiiich hatched on November 24th, 

 and had lived o.n a culture of H. muscae embryos in sterilized faeces 

 since November 28th, the date on \vhich the embryos Avere obtained 

 from a gravid AA^orm. 



The larva (Fig. 8) measures 0.45 mm. in length by about 0.045 

 mm. in Avidth at the anterior end of the intestine. The oesiophagus 

 increases in diameter froin 0.01 mm. at the anterior end to about 

 0.02 mm. at the posterior end. A nerve ring could be seen indis- 

 tinctly at about 0.07 mm,, from the anterior end. The intestine 

 was about 0.18 mm. in length, and slightly narroAA-ed toAvards the 

 posterior end. 



It Avill be noted that the clear space surrounding the pharAmx 

 of both younger and older stages is not shown in this larva. The 

 moulting condition of the anterior end, and the consequent effect 

 upon microscopical appearance may possibly account for the 

 apparent absence of this feature. These remarks may apply also 

 to the larva shoAvn in Fig. 5.. 



The parasite shoAvn in Fig. Avas found, as already stated, on 

 December 3rd, in a fly pupa Avhich harboured the larva represented 

 by Fig. 5, and Avas not more than seven days old. 



