Dr. Griffith on the Sacculi of the Polygastrica. 439 



Prof. Ehrenberg's view, that these vesicles are real stomachs or 

 blind pouches leading out of an alimentary tube, is well known, 

 and has been received for some time. It was founded upon the 

 fact, that colouring and other matters upon which they feed, after 

 having been drawn into the oral orifice of the canal, are next con- 

 ducted to these cavities, where they remain a certain time ; they 

 are then propelled onwards, sometimes into other similar cavities, 

 sometimes through the tract of the canal to the opposite extre- 

 mity of the tube, whence either they or their undigested remains 

 are expelled, or they are ejected by the same orifice at which they 

 entered. Lately doubts have been thrown over these views, and 

 many accurate observers are opposed to the doctrines of Ehren- 

 berg. Having had considerable opportunities of observing these 

 interesting objects under a great variety of conditions, I am 

 convinced that the views of the different authors which I shall 

 presently mention are each generally correct, and that with slight 

 modifications they are readily reconcilable to one another. Pro- 

 fessor Rymer Jones* says, " The positions of the mouth and anal 

 aperture we are well assured by frequent examination to be such 

 as are indicated by the illustrious Professor at Berlin ; but with 

 regard to the tube named by him intestine and the stomachs ap- 

 pended thereto, our utmost patient and long-continued efforts 

 have failed to detect the arrangement depicted in his drawings. 

 In the first place, as regards the function of the sacculi, which he 

 looked upon as organs in which digestion is accomplished : in car- 

 nivorous animalcules which devour other species, we might expect, 

 were these the stomachs, that the prey would be at once 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 having recourse to the result of actual ex- 

 perience, 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 parenchyma 

 has 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 

 of Paramecium aurelia, an animalcule, which from its size is pe- 

 culiarly 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, 

 * ' A General Outline of the Animal Kingdom.' Although these views 

 have been previously extracted into this Journal (vol. iii. p. 105.), as Pro- 

 fessor Owen's observations obviously apply to some part of them, the subject 

 would be incomplete without them. 



