54 THE MICROSCOPE. 



broad as it is long ; a wreath of cilia surrounds both 

 the top and the bottom edges. Now it leaves the 

 hydra, soon, however, to return to it again. The 

 name of this little parasite is Trichodina pediculiis. I 

 am of opinion that these hydra-lice are indicative of 

 a not very healthy condition of their hosts ; but 

 whether they are annoying or not I cannot say. 

 The curiously-formed stinging organs of the hydra 

 seem to be of no service in warding off these minia- 

 ture Trichodina. 



There is one curious creature which I must intro- 

 duce to your notice, and which you may not unfre- 

 quently find in the surface mud of any pond. I shall 

 never forget my first acquaintance with this animal, 

 about twenty years ago. So struck was I with its 

 absurd and grotesque appearance, having at that time 

 but little acquaintance with microscopic forms, that I 

 could hardly believe the evidence of my senses, and 

 I called in a servant to look at the strange creature, 

 and to tell me that I was not dreaming. Well, what 

 was the creature ? It was a Tardigrade, a very " slow- 

 goer" indeed, but the strangest of beasts ; it was 

 something like a naked sloth, only it had four pairs 

 of legs instead of two. These legs such things to call 

 legs were each provided with four claws ; there was 

 no tail ; its mouth was changeable in form, now 

 blunted, now pointed with pouting lips. A curious 

 oval-shaped muscular body, with peculiar style-like 

 appendages was very conspicuous ; this was the ani- 

 mal's gizzard. The style-like processes, or horny rods, 

 are said to be protrusile ; but though I have fre- 

 quently examined tardigrades since I first made their 

 acquaintance, I do not think I ever saw these rods in 

 a protruded state. 



These animals, like the rotifers, are capable of 

 bearing exposure to very great heat without being 



