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original appearance. It is interesting to notice that nioditica- 

 tions take place in this variety of foot as well as in others, 

 whenever the peculiar habitat of the animal may require it.' 



A medical friend brought me some time ago a minute larva, 

 which had been passed from the bowels by one of his patients. 

 I am informed that it is the larva of the " Anthomyia Canicu- 

 laris" a well known fly, and that it has been occasionally 

 passed in enormous quantities, at distant intervals, by many 

 individuals. Though it is found in river water, it does not 

 appear to attain its full growth except in the intestines of 

 man, and probably other animals. 



As far as I have been able to ascertain its habits, it appears 

 to stick the two formidable hooks with which its head is 

 furnished into the mucous membrane. It then forms around 

 itself a tolerably strong tube of agglutinated mucus. This 

 tube is constantly lengthened, either by the passage downwards 

 of the contents of the bowel, or voluntarily by the efforts of 

 the insect. 



Whichever supposition be correct, it is plain that unless the 

 usual claws of the larva foot were kept sheathed or else modi- 

 fied greatly, this elongation could not well take place, as the 

 hooks would constantly arrest its progress. We find that in 

 reality the hooks are entirely wanting, and that their place is 

 taken by a few soft paddles of sufficient strength to be used 

 either to propel the tube backwards or the insect forward, or 

 to take their part in the fashioning of the habitation in its 

 particular way. Fig. 11. 



These paddles are retracted by muscles in the same way as 

 the hooks of other larvae. 



I have only recently been able to procure the fore feet of 

 the bot which attaches itself to the mucous membrane of the 

 stomach of the horse {oestnts equi). This larva, like that I 

 have just described, has its head furnished by powerful hooks, 

 by which it can attach itself firmly to the mucous membrane. 

 Its feet are not required for locomotion and are found to be 



