LEPISMA AND PODUKA. 
Although the Lepisma is usually ranked among the test-objects 
it must be observed that it is one of the lowest order, an instrument 
Fig. 19. 
of the most moderate efficiency never failing to render the striae 
tolerably distinct. 
24. The Podura, or common Spring-tail, is a little insect, gene¬ 
rally found in great numbers in damp cellars, where they may he 
seen, running and skipping about upon the walls. Mr. Pritchard 
recommends the following method of collecting them: Sprinkle a 
little oat-meal or hour upon a piece of blackened paper, and place 
63 
