106 Prof. R. Jones on the Digestive Apparatus of Infusoria, 



in carnivorous animalcules which devour other species we 

 might expect, were these the stomachs, that the prey would 

 at once be conveyed into one or other of these cavities ; yet, 

 setting aside the difficulty which must manifestly occur in 

 lodging large animalcules in these microscopic sacs, and ha- 

 ving recourse to the result of actual experience, we have never 

 in a single instance seen an animalcule, when swallowed, placed 

 in such a position, but have repeatedly traced the prey into 

 what seemed a cavity excavated in the general parenchyma of 

 the body. 



In the second place, the sacculi have no appearance of being 

 pedunculated, and consequently in a certain degree fixed in 

 definite positions : during the last two hours we have been 

 carefully examining some beautiful specimens oi Paramecium 

 aurelia, an animalcule which, from its size, is peculiarly adapt- 

 ed 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, 

 changing moreover their relative positions with each other, and 

 resembling in every respect the coloured granules which have 

 been described as visible in the gelatinous parenchyma of the 

 Hydra. 



With respect to the central canal, we have not in any in- 

 stance 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 circumstances attending the prehension of food 

 would lead us to imagine a different structure ; witness for ex- 

 ample the changes of form which Enchelis pupa undergoes 

 when taking prey, as shown in fig. 16, 3, where it is repre- 

 sented in the act of devouring a large animalcule, almost equal 

 to itself in bulk, and is seen to assume a perfectly diflferent 

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

 its whole body becomes gradually distended. Such a capabi- 

 lity 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 di- 

 gestion is accomplished. 



