64 Gerald F. Hill: 



tivitis," these larvae being regarded by Kailliet and Bull as the- 

 larvae of an e(]uine species of Habronenia. The present writer can- 

 not, however, from the material and evidence so far at his disposal, 

 definitely refer tlie larvae so far seen to any(»ne of tlie three species^ 

 of Habronema, the development of which is herein described. It 

 was at first thouglit when it was found that Stomoxys calcitrans 

 Avas the chief intermediary host of H. microstoma, that Bull (1916) 

 was right in so far as he believed these larvae found by him in such 

 lesions were introduced by a biting insect and that really they were 

 the larvae of H. microstoma. I am indebted to Lewis and Seddou 

 for allowing me to examine their material, and in the only speci- 

 men in which the anterior end is in a sufficiently good condition for- 

 this purpose (their Specimen No. 3), the pharynx of the larva in 

 the lesion is undoubtedly not that of H. muscae, nor apparently 

 that of H. microstoma. It is just possible that it is tliat of a H. 

 megastoma larva, but the other characteristic features of the head 

 of a larva of H. megastoma of this stage of development are en- 

 tirely wanting. So that, as stated above, I cannot regard it as in 

 any way proved that the examples of '' Habronemic conjunctivitis "^ 

 under my notice have been caused by any of the thi'ee equine Habro- 

 nema species. 



Develojmie7it inio adult in Horse. 



Once freed from the fly-host in the stomach of the final host, the 

 " sixth stage " larva develops into the adult in the stomach con- 

 tents in the case of H. nuiscae and H. microstoma; these are pos- 

 sibly kept from being carried away in the ingesta by inserting their 

 heads into the mucous membrane, or at least into the lumen of the- 

 glands. 



In the case of H. megastoma, the larva either finds its way inta 

 a nodule already formed (since, as already stated, the final larval 

 stage has been frequently found with adults in fully formed' 

 tumours or nodules), or else penetrates the lumen of glands, there- 

 setting up the irritation which results in the formation of a new 

 tumour. What determines which of the two shall occur I cannot 

 say. 



Development of next generation in stomach and i7itestine of final 

 host and its faeces. 



As already seen, the eggs containing embryos must be poured* 

 out in considerable numbers into the interior of the nodule in the- 

 case of H. megastoma, and thence into the cavity of the stomach,. 



