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A Comparison of the Metamorphosis op the Crane Fly 



and the Blow Fly. 



By A. Hammond. 



{Read January 28, 1876.) 



I purpose this evening to draw a comparison between the pro- 

 cesses of metamorphosis as they occur in the Crane Fly and the 

 Blow Fly respectively. The anatomy of the larva of the former 

 insect has formed the title of some communications I have lately 

 made to " Science Gossip," and, in endeavouring to continue these 

 observations, by an examination of the pupa, I was influenced by 

 the persuasion that I should find a close parallel in the mode of its 

 development, to that followed in the latter, especially with regard 

 to the re-development of the thoracic segments from a series of 

 structures called by Dr. Weismann, " Imaginal Discs." In this 

 expectation I have, to a certain extent, been disappointed, inas- 

 much as though I recognise the structures, I am doubtful if they 

 represent, here at least, anything essentially exceptional in the 

 mode of development of the segments to which they belong. Still, 

 even if this doubt should be established, I regard it as none the 

 less interesting to note, how in insects which belong to the same 

 order, the perfect form should be reached through processes which 

 widely differ. 



Before proceeding further, however, I wish to say that I come 

 before you more as a learner than as a teacher, and that the opinions 

 I may express, especially where they differ from those who have 

 preceded me, may be the result of imperfect information, and much 

 of what I may say may possibly be already very well known. 



I will now give a short account of the anatomy of the larvae of 

 these two insects, so far as is necessary for our purpose. That of the 

 Crane Fly will be found detailed at length in the papers referred to. 

 In the preparation of these papers, I have been guided solely by such 

 light as Mr. Lowne's " Anatomy of the Blow Fly," and the some- 



