THE MICROSCOPE. 227 



before its legs and wings become rigid; but first have ready a small 

 piece of glass, on the surface of which spread a thin film of rather 

 stiff Canada balsam. Then place the fly, or any other insect you 

 may be operating on, lightly upon the Canada balsam film in the 

 position you desire. If a dorsal view is required, and a winged 

 insect the subject, place it back upwards, then with a fine needle or 

 pin arrange its legs and wings. The legs may be made to adhere 

 their entire length to the ba*lsam, but it is desirable that only the 

 tips of the wings be held down by the balsam. In this position the 

 insect should remain for two or three hours to allow the balsam to 

 become harder and the limbs of the insect stiffer. Then place the 

 piece of glass with the insect adhering to it in spirits of wine, where 

 it should be allowed to remain for two or three days. It is not un- 

 likely that in the course of a few hours the action of the spirits may 

 cause the film of balsam to become detached from the glass. This 

 will not matter, for the hardened film will be found sufficiently dense 

 and strong to keep the legs and wings of the insect in the position 

 they were originally placed in by the setting needle. Should, how- 

 ever, the film not become detached when it is time to withdraw the 

 piece of glass from the spirits, it is easy to remove the insect by 

 placing the piece of glass in spirits of turpentine, which will dissolve 

 the hardened balsam. If, as mentioned before, the film has become 

 detached from the glass, a few hours after its first immersion in the 

 spirits, it should remain undisturbed in the spirits for some days, 

 and then it can be treated with turpentine. It should be kept in 

 clear spirits of turpentine until it has become sufficiently transparent 

 for mounting in Canada balsam. 



There are some species of spiders that will crumple up their 

 legs unless pinned out. The pinning out is "not at all a difficult 

 process; it merely takes a little more time. Fasten with fine tin wire 

 a thin cutting of cork to a piece of glass, then spread a thin film of 

 Canada balsam on the cork. Lay the spider in position on the 

 balsam, and having previously cut the points of a number of fine 

 pins, take the points up with a pair of light forceps and stick them 

 into the cork against the inner side of the legs of the spider. One 

 point, if properly placed, will be sufficient for each leg. The palpi 

 and mandibles may also be kept in position in the same way. After 

 this has been accomplished put the whole in spirits of wine and fol- 

 low out the treatment described for flies. The piece of glass must, 



