38 INFUSOKIA. 



pedunculated and consequently in a certain degree fixed in definite 

 positions : we have just been for two hours carefully examining some 

 beautiful specimens of Paramecium Aurelia (fig. 1 6, 4), an animalcule 

 which, from its size, is peculiarly adapted to the investigation of these 

 vesicles ; and so far from their having any appearance of connexion with 

 a central canal, as represented in the figure copied from Ehrenberg, they 

 are in continual circulation, moving slowly upwards along one side of 

 the body, and in the opposite direction down the other, continually 

 changing their relative positions with each other. 



(77.) With respect to the central canal (fig. 16, 2, 3, 4), we have not 

 in any instance been able to detect it, or even any portion of the tube 

 seen in the figures, much less the branches represented as leading from 

 it to the vesicles or stomachs, as they are called. Even the circum- 

 stances attending the prehension of food would lead us to imagine a 

 different structure ; witness, for example, the changes of form which 

 JZnchelys pupa undergoes when taking prey, as shown in Ehrenberg's 

 figure, where it is represented in the act of devouring a large animalcule, 

 almost equal to itself in bulk, and is seen to assume a perfectly different 

 shape as it dilates its mouth to receive the victim, with which its whole 

 body becomes gradually distended. Such a capability of taking in and 

 digesting a prey so disproportionate would in itself go far to prove that 

 the minute sacculi were not stomachs, as it evidently cannot be in one 

 of these that digestion is accomplished. 



(78.) Since the above was written, the views of Professor Ehrenberg 

 relative to the organization of the nutritive organs of the so-called Poly- 

 gastric Infusoria have been combated by many zealous observers both 

 in this country and upon the Continent, and appear now to be univer- 

 sally abandoned. Mons. F. Dujardin* attributes the formation of the 

 internal cells observable in the interior of these animalcules to the pro- 

 perties of a peculiar glutinous animal substance resembling living jelly, 

 of which he supposes the lower organisms to be principally composed, 

 and which he calls sarcode. This substance, according to the views of 

 M. Dujardin, spontaneously produces in the interior of its mass vacuoles f 

 or little spherical cavities, into which the surrounding water finds 

 access, and conveys along with it the coloured particles, but having no 

 regularity of arrangement. 



(79.) According to the views of M. Dujardin, the phenomena attend- 

 ing the passage of aliment into the bodies of the so-called Polygastric 

 Infusoria may be described as follows as they occur in Amphileptus. 

 In the interior of the body there are generally perceptible five or six 

 vacuoles or cavities, distended with water, in which are contained 

 monads and other substances swallowed as food. These vacuoles change 

 their situation, advancing gradually towards the posterior extremity 

 of the animalcule, where may be observed a vacuole or vesicle of 

 * " Eecherches sur les Organismes inferieures," Ann. cles Sc. Nat. 1835. 



