284 F, ADDEY ON VERTICAL DIMENSIONS OF OBJECTS. 



it is a fair assumption to consider that the claws on correspond- 

 ing legs are equal to one another, we have thus two equal objects, 

 one lying across the line of sight, and one lying at right angles to 

 it. A camera-lucida drawing of the claws is shown in Fig. 5. The 

 length of the claw lying across the line of sight was measured with 



Fig. 5.— Hind claws of cat flea, Ctenocephalus felis. X 250. 



the eye-piece micrometer, while the vertically directed one was 

 measured with the graduated fine adjustment. 

 The results obtained were as follows : 



Vertically directed claw : 

 3'25 divisions = 3*25 X 20jti = 65*0 /a apparent length. 

 65-0 X 1476 (the refractive index of glycerine) = 95*8 //.. 



Transversely directed claw : 



Micrometer measurement = 93*15 //,. 

 This again confirms the theory given above. 



Journ. Quekett Microscopical Club, Ser. 2, Vol. XIV., No. 88, November 1922. 



