430 Gerald F. Hill: 



The Adult. 



In the adult stages H. inierostuiua bears a very close similarity 

 .to H. imiscae, but the species are distinctly different, and, after a 

 little experience may be easily sepai'ated, even Avhen living. 



Although ^vell known in Victoria, it is not so fre<iuently met with 

 iis its near ally (H. muscae) as will be seen from the results of the 

 'Census of tlie parasites found in tiiirty-nine horses' stomachs 

 examined during the progress of these investigations (c.f. Table 

 No. 9). Whereas H. muscae were found in thirty-three stomachs, 

 H. microstoma were found in only fourteen. In all cases in which 

 both species were found in the same stomach the former greatly 

 'Outnumbered the latter. 



It will be noticed in Table No. 1) that H. microstoma were not 

 found in eleven stomachs examined in the months May — August. 



As Ransom has fully described and figured the adult H. micros- 

 toma (1913, p. 27), it is unnecessary here to enter into details of 

 tlie structural and diagnostic characters of the species. 



Record of Expepiments and Special Observations. 



A. To determine the intermediary host or hosts of H. microstoma 

 and the early life-histoi-y of the parasite. 



The technique followed in these experiments has been fully de- 

 ;6cribed in the Introduction to this Report. 



Ecperimerif No. 7. 



On October 2r)th embryos from twenty gravid H. microstoma 

 Avere libei-ated in sterilized faeces with a numl>er of "clean " four- 



^days' old Musca domestica larvae. Twenty-two of the fly larvae 



^vere examined on October 29th and the first two days of November. 



'One of them was found to haibour a single end^ryo similar to that 

 seen in Figure 20. The remainder of the larvae were not found to 

 be infected. Twenty-seven pupae and twenty-two flies from the 



i^ame culture jar examined between October 'Ust and November 7th 

 were not infected. 



Experiwe?>f No. 8. 



Embryos from five worms Avere liberated in faeces on Novend)er 

 •26th, with a number of Musca domestica larvae then three days 

 old. Five larvae. 57 pupae and .35 adult flies Avere examined be- 

 tAveen November 29th and December 11th, of Avhioh only one larva 

 -Avas found to be infected (November 29th). The embryo found in 



