310 GENEEAL HISTOKY OF THE INFUSORIA , 



fiiniiel- shaped tube, often delicately plaited longitudinally, and suiTounded 

 ■with cilia. Ai'titicial feeding was tried ; but no colouring particles were swal- 

 lowed. The existence of a digestive power is sho^syn by the disappearance of 

 organic matters which have been swallowed, leaving little or no residue un- 

 absorbed. Thus other smaller animal organisms are often the prey of Ciliata ; 

 and their gradual absorption into the general mass may be occasionally 

 watched : the same, too, is true of vegetable matters such as Diatomece, Des- 

 midiece, portions of Oscillatorice, and of various minute Algae, — although here 

 a certain amount of miassimilated matter in the hard lorica or valves remains 

 over and above, to be subsequently got rid of. The changes ensuing in food 

 during the act of digestion are illustrated by Ehrenberg in his account of 

 Bursaria vernalis. This animalcule feeds very much on OsciUatorice ; and on 

 watching the fibres, they are seen, when first swallowed, to be elastic, rigid, 

 and of a beautiful bluish-green colour, but presently they become lax and 

 of a bright green hue, which afterwards changes to a yellowish green, and 

 ultimately to a yellow, the filaments at the same time breaking up into de- 

 tached joints. 



An assimilative function is evidenced both by the foregoing facts of the 

 absorption of foreign organized matters, and also by the circumstances, that 

 the magnitude acquired and the activity of other functions are regulated by 

 the quantity of nutriment received, and that after certain substances have 

 been taken as food they may be detected in certain parts, or thi'oughout the 

 tissue of the animalcule. Of the latter, the introduction of chlorophyll into 

 the subtegumentary tissue, by the medium of food containing this vegetable 

 constituent, is an example ; and in general the colom^ of an animalcule depends 

 directly on the food taken, or is indirectly influenced by its quality and 

 quantity ; for an animal well nourished always exhibits its pecuHar colour 

 in the highest degree, whilst ill-nouiished sickly examples present little or 

 none. 



This topic suggests another closely allied to it, viz. the artificial feeding 

 with coloured substances, so much resorted to by Ehrenberg in his researches. 

 It consists in the introduction of a very small quantity of some insoluble 

 coloiu', not a poison, capable of minute division, into the water in which the 

 animal floats whilst under observation. The colours generally employed are 

 indigo and carmine, a Httle of one or other of which is rubbed on the wet 

 margin of the slide, sui^rounding the thin glass cover, whence it gradually 

 steals under the cover, and disperses its flne particles through the little drop 

 in which the animalcule floats. 



Another substance has been proposed as preferable, by Mr. Thomas A\Tiite 

 (J. M. S. 1854, p. 282), viz. the red eyes of the common fly, reduced to fine 

 powder by pressm^e. By feeding animalcules with this in heu of carmine, the 

 disadvantage aiising fi'om the dark particles of the latter crowding the field of 

 view and obscuring the objects is obviated ; and, on the other hand, it has the 

 actual advantage of being more readily imbibed, and therefore of appealing 

 more speedily in the apparent stomach-sacs. 



Ehrenberg imagined that the Cihata enjoy the sense of taste, leading them 

 to choose or refuse at ^vill among articles of nourishment within theii* reach. 

 Thus he says that, amidst a number of inchviduals of Paramecium Aurelia, 

 some took one sort of food, and others another, — no doubt a correct observa- 

 tion, but insufficient to prove the existence of taste. Nevertheless it must be 

 allowed that some animalcules are especially found in company either with 

 certain other small animal organisms, or with particular plants, or in water 

 holding certain matters in solution, — a fact upon which our knowledge con- 

 cerning their habitats and modes of life rests, but in itself no proof of the 



