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SOME HAIRS UPON THE PROBOSCIS OF THE BLOW- 

 FLY. 



By Edward M. Nelson, F.R.M.S. 

 Read December 20t/i, 1907. 



It has been truly said that the proboscis of the Blow-fly is one 

 of the most interesting of microscopical objects, and, like the 

 Podura scales, it has already been examined by such an army 

 of observers that it is scarcely possible for us nowadays to dis- 

 cover anything that has not been seen a hundred times before. 

 At the time I began to be interested in the microscope, the Blow- 

 fly's tongue, squeezed flat, as mounted by Topping, was a common 

 test for low-power objectives, the test being the sharpness of the 

 " Zebra marks ' at the root of the cut suctorial pipes.* I 

 suggested that the minute spinous hairs upon the upper surface 

 of the sucker would make a more suitable test, and they have 

 since been largely used for that purpose. Thpse spinous hairs are 

 very interesting, inasmuch as they admirably illustrate nature's 

 adaptation of a means to an end. It is neccessary that the upper 

 surface of this very delicate membrane should be protected while 

 the insect is feeding, and it is also necessary that the means of 

 protection should neither overload the membrane nor interfere 

 with its pliability. Nature, however, has found a way out of the 

 difficulty. She has studded the membrane with quantities of very 

 small spinous hairs. These hairs are so minute as not to impair 

 the flexibility of the membrane, either when expanded and in use, 

 or when flaccid and withdrawn ; at the same time, being curved, 

 they form a better protective covering than they would if they 

 were straight. 



The visibility of the filamentous ends of these hairs is not only 

 a test, but affords excellent practice in minute microscopical 

 work, which one should undertake before attempting the more 

 difficult examination of the flagella of bacteria. It was stated 

 above that these hairs were spinous ; there are, however, other 

 hairs equally minute upon the rostrum which are of a totally 

 different character, being pliant and soft. Besides these minute 



* Illustrated by W. T. Suffolk, M. 31. /., vol. i. 1869, pi. 16, fig. 2. 



