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 stria> 

 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 be 

 seen, running and skipping about upon the walls. Mr. Pritchard 

 recommends the following method of collecting them : Sprinkle a 

 little oat-meal or flour upon a piece of blackened paper, and place 



