6 



THE MICROSCOPE. 



Jan., 



whale-bone, three inches long and about one fourth inch 

 in width, hold the end over the lamp and when it is 

 warm it can be cut easily. Shape each piece nearly to 

 a point as in Fig. 1, being sure to have them smooth at 

 the points and of exactly the same shape. About one 

 half inch from the other end cut a little notch in each 

 edge having the notches exactly correspond when the 

 pieces are put together, tightly bind the two pieces to- 

 gether by strong thread, 

 putting the thread in the 

 notches that it may not ^-c: 

 slip. Carefully bend the 

 pieces so that the two-^ 

 points will stay one half 

 inch apart. 



Notice that the legs of 

 the fly are covered with 

 stiff black hairs and that 

 these are quite numerous 

 on the tarsi, and that the 

 foot is furnished with two 

 hooks (Fig.3,H.) Under 

 these hooks are two mem- 

 braneous expansions or 

 pulvilli, these are beset 

 with hairs, and are in 

 some way connected with its power to walk on the 

 smooth surfaces in opposition to the force of gravity. 

 Recent investigation has led to the belief that these 

 secrete a gelatinous substance, the adhesion of which 

 enables the fly to walk on the walls and ceilings and the 

 two hooks are used to aid in detaching the foot, as we tear 

 off a porous plaster, and the reason the flies remain 

 hanging to the windows in the fall is because in their 

 weakened condition they have not the strength to de- 

 tach their feet. 



