56 



that the parent animal could have been accidentally swallowed, and 

 its ova, previously impregnated, have become developed in the bow- 

 els ; though this is perhaps the least objectionable supposition. At 

 any rate the parent animal could not live in the alimentary canal, 

 since the larva has been recognised by several entomologists as being 

 that of a well-known fly, (the Anthomyia canicularis). The latter 

 supposition however which I have advanced, namely, that the fly, 

 having its eggs previously impregnated, may have been swallowed, 

 and thus, perishing in the digestive canal, have left the ova unencum- 

 bered, and in a possible situation for development, derives some coun- 

 tenance from the circumstance of the extreme rarity of the occujrrence 

 of these larva? as parasites, there being, as I have mentioned, very 

 few cases on record ; which would give to the circumstance the air of 

 an accidental occurrence, of which however it is again immediately 

 robbed when we contemplate the singular and very obvious adapta- 

 tion of its organization to the peculiar circumstances in which it is 

 thus placed. The anatomy being clearly that of an animal destined, 

 or at least adapted, to live by adhesion and suction on fluid nourish- 

 ment, though it is clear from the fact of some being found nearly two- 

 thirds grown in simple river water, that the larva is also capable of 

 life and growth in other elements than the contents of the alimentary 

 canal, and in other capacities apparently than that of a parasite. 



Much, it appears, may be advanced on either side, and indeed the 

 whole subject appears to me to be calculated to afford interesting 

 points for discussion ; and it is chiefly with this view that I have 

 brought it before the notice of the Society. 



