3^4 Ettraordhiaty Mimiteness of the Infusoria. 



By means of the microscope, I saw distinctly monadesin which 

 the greatest diameter of the body was from j/ou'" ^^ 55^00'" o^ ^ 

 line. This, which is the smallest of known animals, I have named 

 Mmas termo, is the same as that described by Otto F. MuUer, 

 under this name. In the largest individuals of this animal, I 

 was able, by colouring the liquid, to discover in some, the lar- 

 ger, six, in the smaller, four sacs or stomachs ; and in some 

 of them the stomachs did not occupy the half of the whole 

 animal. Such a stomach of the Monas termo, therefore, if 

 the animal is only j-^^-^ part of a line in size (if there are 

 only four stomachs which occupy the half of the animal), 

 is 1^3 J 00 P^^t of a line in magnitude, consequently five times 

 smaller than the smallest molecules observed by R. Brown. We 

 observe in the forepart of these animals, as in all the monades, 

 a violent projection of still smaller bodies than itself, as soon 

 as these come near to it, hence these have probably a wreath of 

 ten or twenty feelers around the anterior mouth opening, as in 

 the Monas pulvisculus, and the other still larger monades. It 

 is probable that each of the stomachs which are filled in our 

 experiments with colouring matter, contain more than one 

 atom; if each stomach contains three coloured atoms, this af- 

 fords a proof of the existence of red and dark blue particles 

 of colouring matter floating in water, with a magnitude of 

 jsoou P^^t ^^ ^ l^"^j 175000 P^^^ of an inch in diameter ; and 

 if the same objects are calculated according to the smallest ani- 

 mals we have observed, which are ^^\q of a line in magnitude, 

 and sometimes contain four coloured points in the hinder part 

 of the body, these latter parts, which are no longer individual- 

 ly distinguishable, even by a power of 800, but are distinguished 

 in the aggregate, have a magnitude of 4^Joo ^^ ^ ^'"^? ^^ 

 JT60150 of ^^ ii^chj which is twenty times smaller than the 

 smallest molecules of R. Brown. We may also notice the fine- 

 ness of other parts of these living' organic beings. The small 

 stomachs of the monas appear isolated in the body, and sharply 

 bounded. In larger infusoria which are ■^/", or upwards, in 

 diameter, we see these receptacles as distinct bladders, and there 

 is no reason for assuming another structure in the coloured ca- 

 vities observed in the smallest of the monades in our experi- 

 ments. If we assume the thickness of the walls of the stomach 



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