LARVA OF CRANE-FLY. 



177 



from it without tearing the whole to pieces. The sting, 

 lancet, and poison-bag of wasp may be seen in Fig. 163. 



The object of dissecting, after all, is not to be able to 

 prepare pretty slides merely, 

 but to gain a knowledge of the 

 anatomy of our subject, so 

 that we may understand more 

 thoroughly the various trans- 

 formations which take place. It 

 may not be possible always to 

 isolate each organ we wish, and 

 in that case a careful study 

 should be made of the organs 

 in situ sometimes by polarised 

 light, and what we have actually 

 seen may be transferred to paper 

 by any of the methods described 

 in the chapter on " the Delinea- 

 tion of Objects." 



An instance of this may be 

 found in Fig. 164, where the 

 internal organisation of the larva 

 of the crane-fly is delineated. 

 To lay out the various organs as 

 there shown would be a task of 

 supreme difficulty ; but a draw- 

 ing may be made of them from 

 the student's observations. 



Another study having an in- 

 terest with many is that of the 

 tongues, palates, lingual ribbons, 

 or odontophores, of molluscs. FlG ' l64 ' 



The subjects for dissection should be killed by drop- 

 ping them into glycerine, and so preserved until they are 



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