ITS FRIGHTFUL ASPECT. 355 



To clear up the mystery of a movement whose cause is 

 not apparent at the first glance, let us sprinkle with this 

 impalpable debris, with this kind of sawdust, or cheese- 

 dust, a little strip of glass, and place it beneath the focus of 

 a microscope. 



Ah ! you exclaim, what a frightful creature ! These long 

 sharp cilias seem to be so many lancets covering the whole 

 body, and especially the legs ; its head, like that of the 

 harvest-bug, protrudes and recedes under a transparent cara- 

 pace ; thus communicating to the 

 animal something of the aspect of 

 a turtle. In all other respects its 

 form exactly resembles the harvest- 

 bug; only its body is more elongated 

 towards the anterior extremity than 

 that of the latter. While the harvest- 

 bug makes us think of a spider, the 

 body of the Acarus has a greater 

 likeness to an insect's. (Fig. 77.) 

 Yet the Acarus has eight legs, like a spider, and the harvest- 

 bug six, like an insect. Attempt, then, to establish your 

 absolute rules ! 



Let us continue our observation of this cheese-worm. The 

 well-defined thorax forms nearly one-third of the fore-part of 

 the body, which is of a shining whitish-red or reddish-white. 

 The proboscis, shaped like a conical tube, is armed with two 

 projecting mandibles, which, like true pincers,, can be brought 

 close together, or moved wide apart, thrust forward singly or 



