240 ROMANCE OF LOW LIFE AMONGST PLANTS. 



people, that when flies killed by this disease fell by 

 accident or were intentionally cast into water, they 

 developed from their bodies another and quite distinct 

 kind of aquatic mould, which was identical with that 

 causing the salmon-disease. If this were a fact the 

 inference would be that, if a fly which had been 

 destroyed by the common fly-mould, Empusa ihusccb, 

 came in contact with water, the result would be 

 the conversion of the fly-mould into the salmon- ' 

 moulds, Saprolegnia ferax or AcJilya prolifera. In 

 these latter days such a belief as to the transmutation 

 of species, so distinct and definite in their character, 

 obtains little credit. Whilst the existence of the fly- 

 mould, and also of the salmon-mould, upon flies and 

 other dead insects is not denied. 



Our principal concern is with the fly-mould, 

 which may be accepted as the type of certain insect 

 parasites known as the Eiitouwphthorecs, of which 

 a more detailed description is necessary. It may be 

 premised that the frosted condition, and cloudy halo, 

 above alluded to are caused by the external conidia 

 of the mould, by means of which the species is dis- 

 seminated. There is also, in addition, a mode of 

 internal propagation, by the . production of thick- 

 walled resting spores, which, after a period of rest, aid 

 in the perpetuation of the species. So that the fly- 

 mould may be communicated by conidia, and also 

 by resting spores. It has not yet been demonstrated 

 that infection results from the inception of the conidia 

 with their food by healthy insects, but by external 

 application. 



The conidium attaches itself to the surface of the 



