262 EVENINGS AT THE MICROSCOPE. 



Between the two middle spines the shell is cut into 

 a deep notch, out of which protrudes, when the wheels 

 are expanded, a curious little organ, consisting of a 

 couple of fleshy tubes, the one sheathed in telescopic 

 fashion within the other, and bearing at its tip a pencil 

 of bristles, which can in turn be sheathed. This organ 

 doubtless represents the united antennae of Insects. 



But, you ask, what is that much more conspicuous 

 organ that is alternately thrust out and drawn back at 

 the bottom of the shell, and that is so nimbly whisked 

 about in all directions, looking, with its numberless 

 transverse wrinkles, and its little fingers at the tip, so 

 like an elephant's trunk in miniature ? This is the 

 creature's foot ; the only one he has ; and as I said the 

 little tubular telescope represents the two antennae fused 

 into one, so we must consider that this flexible member 

 represents all the six pairs of an Insect's legs united, 

 or perhaps, more philosophically, one of the pairs, the 

 rest being obsolete. It must not be considered as a tail, 

 not only from its function, which is decidedly that of 

 locomotion, but also from its position on the ventral 

 side of the intestinal orifice. It is a curious organ, 

 capable of great elongation or, at the will of the animal, 

 of entire retraction within the abdomen ; and this in an 

 instant : while, as you observed, it is flung about, and 

 dashed from side to side, and bent hither and thither 

 with a sort of insane energ3\ The means by which 

 these movements are performed, you may easily discern 

 in several pairs of muscular bands which run through- 

 out its w^hole length, their upper insertions being placed 

 high up on the interior of the shell, where, during con- 

 trastion, you may see them swollen into thick bulbs. 



Tlie foot terminates in two short conical fingers oi 



