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XXV. The Foot of the Fly ; its Structure and Action : elucidated hij comparison with 

 the feet of of her Insects, 8fc. — Part I. By Tufpen West, I]sc[., F.L.S. 



Read March 21st and June Gth, 186 1. 



The structure and action of the Fly's foot have been so frequently treated of, and are 

 so generally considered to be fully understood, that it may appear, at the first glance, as 

 if nothing further could be done with so hackneyed a subject. Whilst, however, in con- 

 sequence of some investigations which have been recently made to determine its structure, 

 opinions jnay now be considered as pretty well fixed with regard to this portion of our 

 subject, authorities still differ widely respecting the action of the parts of which the foot 

 is composed. Nor has it appeared that any satisfactory progress was making toAvards a 

 reconcilement of the differences of opinion on the subject, — each succeeding author setting 

 aside, more or less, the opinions of his predecessor in point of time, only to be himself 

 again contradicted by his successor. On reflection, it occiirred to me that this probably 

 arose in great measure from the attention of observers having been confined too exclu- 

 sively to the Flf's foot, and that perhaps, amongst the teeming myriads of insect-life, 

 structures might, on careful search, be met with resembling those under consideration in 

 every respect but that of their being on a larger scale. Supposing this to be the case, 

 the advantages gained, b6th for purposes of observation and of reasoning, will be very 

 great, as will be best appreciated by those who have had large experience in micro- 

 scopic researches on very minute parts. The high powers necessary for investigations 

 under such circumstances demand so many appliances in the instrument of research, with 

 such great sldll in the use of them — all these tending to introduce new sources of error — 

 that the student feels it a relief indeed when he can assist his mind tov,-ards forming con- 

 clusive opinions by availing himself of larger examples of similar structures. That this 

 advantage may be gained in the present instance will appear to some extent during the 

 course of the following remarks, and still more strongly when I come to speak, on a 

 subsequent occasion, of other modifications of the parts noAV to be noticed, of the types 

 of feet in Insects which characterize, with few exceptions, the grand divisions in a syste- 

 matic classification, and of the analogies and homologies respectively of the parts. It 

 is intended now simply to indicate the leading divisions of the subject, and to show that 

 parts similar to those on the Ely's foot, but on a larger scale, are to be met with abun- 

 dantly in other insects. And, this advantage being gained, it is hoped that a fuller un- 

 derstanding of the nature and purposes of these structures jn the insect economy will also 

 be reached, and that the conclusions to be drawn will, fronl the wider basis on which 

 they rest, satisfy more completely than hitherto all the conditions of the question. 



It will be necessary to give a brief sketch of thQ labours of previous observers on this 

 subject, before stating the results of my own investigations. 



The earliest mention which I find of any minute examination of the feet of the Ely is 



