118 EVENINGS AT THE MICEOSCOPE. 



are inhabitants of our fresh waters : the chameleon-grub 

 lives in ponds, crawling among the stems of aquatic 

 plants, and occasionally visiting the surface in the man- 

 ner you have seen ; but it is precarious — in some sea- 

 sons not uncommon, in others, scarcely to be met with 

 by the most persevering search. For my next specimen, 

 I have but to go with a basin to the water-butt in the 

 yard, and take a dip of the surface-water at random : I 

 shall be pretty sure of a score at least. 



Here they are swarming, as I told you. What, 

 those things ? why, they are gnat-grubs. "Well, don't 

 despise them, you will find them worth looking at. I 

 dare say you have never submitted them to half-an- 

 hour's microscopical examination. I have caught one 

 with a spoon, and put it into this narrow glass trough 

 of w^ater that it may rest conveniently on the stage. 



We wall take a cursory glance at its entire person. 

 Here is a flat, roundish head, a great globose, swollen 

 thorax, and a long, slender, man^'-jointed body, ending 

 in a curious fork. But all is curious : — the head, with 

 its horny transparency ; its pair of rod-like antennae, 

 covered with minute points ; its two black eye-patches ; 

 and its jaws, beset w^ith strong, curved hairs, set in 

 radiating rows, and, ever and anon, working to and fro 

 with the most rapid vibrations : — the thorax, — so trans- 

 parent, w^ith its amber-like clearness, that you can dis- 

 cern the dorsel vessel, which contains the blood ever 

 dilating and collapsing with the most beautiful regular- 

 ity ; and, beneath this, the gullet, through which, now 

 find then, descends a dark pellet of food, to join the 

 mass already lodged in the stomach farther down, — a 

 result, by the way, that explains that incessant vibra- 

 tion and pumping motion of the mouth-organs, which 



