30 NATURAL HISTORY 



ance. Ehrenberg, on the contrary, having always found 

 them both in the same infusion, and when fed with co- 

 louring matter to be alike, considers them identical: 

 Muller probably inferred a difference, from observing 

 some that had taken opaque food, and others without. 



This creature is much larger than the M. termo^ being 

 from 1 -6000th to 1 -3450th of an inch in diameter, though 

 more commonly of the latter size. A group of them is 

 represented at Fig. 2, magnified 380 times in diameter. 

 It is the smallest animated being in which the mode 

 of propagation has been distinctly recognized : this is 

 effected, when the animalcule has attained to maturity, by 

 a transverse division into two distinct beings : when this 

 is about to happen, the form of the creature first changes 

 from globular to egg-shaped, gradually elongating in 

 one direction ', then a contraction is observed across the 

 middle of the body, as shewn in some of the figures of 

 the drawing, and, finally, the animalcule separates into 

 two. During these changes in its form, it has been 

 mistaken for another species, which shews the cau- 

 tion which should be used in microscopic observations. 

 The age at which they multiply probably depending on 

 their food and the state of the weather, has not yet 

 been determined. The digestive cavities, when filled 

 with colouring matter, are readily seen, and, indeed, are 

 often shewn by their natural food. They have some- 

 times been seen to swim in company, and even to appear 

 as if connected ; in which particular they resemble the 

 young of the Kolpoda cucuUus, only occasionally sepa- 



