126 NATURAL HISTORY 



Tradiscantia Virginia, but omitted to measure it. The 

 magnifying power employed was about 400 : it has a 

 cluster of strong cilia under the neck^ like a beard. 

 252. Trichoda proteus. The changeable Trichoda. 



253. versatilis. — These two species of Muller 



are probably only varieties of the same ', the latter was 

 found in sea- water, the former in fresh river- water. In 

 form it resembles the swan Vibrio, and like it the neck 

 is capable of great extension and contraction ; sometimes 

 exceeding in length that of the body ; at others so con- 

 tracted as to be invisible, and the part of the body from 

 which it protrudes only occasionally discernible by a 

 cluster of cilia around the head : these produce a strong 

 current of water towards it : the posterior extre- 

 mity is pointed, and the creature is about l-60th of an 

 inch in length when the neck is contracted. It was dis- 

 covered by Baker, in the slimy matter which covered the 

 surface and adhered to the sides of vessels containing 

 water snails, small fish, and larves. Baker, when he 

 discerned it, was highly delighted at its changes and 

 movements. It is certainly an admirable object for the 

 microscope, and no doubt, with the assistance of coloured 

 particles, in a good instrument, much of its internal 

 structure might be ascertained. 



254. Trichoda gibba. The hunch-back Trichoda. — 

 This animalcule is convex on the upper side and plane 

 beneath : it is like the Trichoda fasciola, figure 16/. 



255. Trichoda /oe^fl. — This is a spindle-shaped ani- 

 malcule, with the anterior extremity longest, and fur- 

 nished with a few cilia : it can contract itself into a 



