14 The Microscope. 



should be picked up and shaken over a bit of white cloth ; then 

 upon picking up the larger pieces the minute insects can be 

 readily seen. Forms on living plants may be obtained by beat- 

 ing, a process familiar to all insect collectors. The specimens 

 should be kept in alcohol, or, if desired, they can be mounted on 

 slides. One of these insects is familiar to microscopists under the 

 generic name Pochira, its scales being a favorite microscopical 

 test object ; but others of the group are far more handsome than 

 this one, and from the fact that they are the lowest of six-footed 

 insects a careful study of them will give one a good idea of the 

 essential points of insect anatomy. Our American species have 

 scarcely been touched, the only paper of any importance being 

 that by Dr. A. S. Packard noticed below. It will well repay 

 any one to study these forms and in doing this he should have 

 the more prominent works relating to them. Of these the most 

 important is Sir John Lubbock's Monograph of the Collembola 

 and Thysanura, published by the Ray Society and illustrated 

 with nearly eighty plates. Next in order comes Dr. Packard's 

 Synopsis of the Thysanura of Essex county, Mass., published 

 in the fifth annual report of the Peabody Academy of Science 

 (1872). The student, however, should not neglect the litera- 

 ture of the European forms, for many species are common to 

 both continents, and hence the writings of Tullberg, Meinert, 

 Brook and Nicollet should be consulted. Brook's papers have 

 appeared in the Journal of the Linnean Society ot London, while 

 those of Meinert are published in Denmark, and those of Tull- 

 burg in Sweden. In this connection should also be noticed 

 those forms which are now associated here and which form the 

 genus Scolopendrella. In shape they are much like a centipede 

 but their size is much less; in reality they have but little affin- 

 ity to the centipedes. Our forms have been described and fig- 

 ured by Ryder in the Proceedings of the Philadelphia Academy 

 ot Natural Sciences, and by Packard in the American Natural- 

 ist. Researches in the anatomy and development of any of 

 these forms carried on by means of sections would prove very 

 interesting and very important. 



Development of the Leech (Clepsine). — Several persons 

 have studied the development of the various species of leeches, 

 the most valuable paper being that by Whitman (Q, J. M. S. 



