OF ANIMALCULES. 77 



presents the animalcule at rest. In swimming, tlie tail 

 is seldom deflected : the mouth, oesophagus, and alimen- 

 tary canal, are readily distinguished under a power of 

 200. Found in river- water. 



Vibrio anguillula. — This name is applied by Mullerto 

 the four following species of eel-like animalcules : — 



124. Vibrio aceti. The vinegar Vibrio, or Eels in vi- 

 negar, are thread-like animalcules, found in common 

 vinegar exposed to the air for some time, and become 

 slightly turbid. This species is generally longer than 

 the paste eels, but their diameter considerably less : this 

 circumstance, and the agility of their movements, render 

 it very difficult to discern their internal structure ; yet 

 an alimentary canal has been observed, and it has also 

 been ascertained that they are oviparous at one season 

 and viviparous at another. Some trace of an external 

 process has been seen, probably a sexual organ; in other 

 respects they so closely resemble the paste eels that it 

 is unnecessary to give a figure of them. 



From the experiments of Dr. Power, it appears that a 

 slight elevation of temperature above blood-heat destroys 

 them, ^vhile the most intense cold to which he subjected 

 them only produced torpor, although the vinegar was 

 frozen, and become solid : on thawing, they always re- 

 vived. If the surface of the vinegar is covered with oil, 

 and then frozen, the eels will ascend into the oil during 

 the congelation, and return to th? vinegar on assuming 

 a liquid form. If a few drops of sulphuric acid be mixed 



