176 M. F. Diijardin on the Digestive Organs of Infusoria. 



which ought to have been persistent, I now again repeat, and 

 the more so, as M. Ehrenberg insists more strongly on the 

 great contractibiUty * of this intestine to explain the reason 

 why it is never seen in a large number of species : ^' it is,^' he 

 observes, ^^ because this canal, Uke the oesophagus of larger ani- 

 mals, serves merely for the passage of the aliments, and not 

 to contain or digest them, wdiich takes place solely in the 

 stomachic vesicles : it dilates at will for the passage of the nu- 

 triment like the small mouth or throat of a serpent when swal- 

 lowing a rabbit, and contracts immediately afterwards and 

 becomes entirely invisible if not in action/^ But, it may be 

 said, if the indefinite contractibility of the stomachic vessels 

 and their digesting action be admitted, we may suppose them, 

 with greater reason, to have a rather complex membrane, and 

 containing as many, if not more fibres, than the intestine ; now 

 these vesicles on their decomposition by diffluence never show 

 any fibres. We must therefore conclude either that the con- 

 traction is effected without fibres, or that these fibres are 

 really invisible in the vesicles as in the intestine. I shall pre- 

 sently show that the vesicles must be regarded as vacuities 

 excavated at will in the gelatinous substance of the interior, 

 and that consequently they are without any peculiar mem- 

 brane, and contract by the approximation of the mass ; I shall 

 state that the alleged diaphanous vesicles observed at the ex- 

 terior of the body of the Infusoria are nothing more than glo- 

 bules of sarcode, expelled by expression, or by laceration, or 

 by the diffluence of the body of the animalcule, as proved by 

 their refraction and by their faculty of decomposing in exca- 

 vating vacuoles ; but there is a single fact mentioned by Dr. 

 Ehrenberg in his third memoir in 1833, and which I had not 

 been able to understand in 1836, ^ Ann. Sc. Nat.' April 1836, 

 any more than at present. It relates to a stomachic vesicle 

 expelled from Bursaria vernalis decomposing by diffluence, 

 and W'hich still contained two fragments of Oscillatoria, It 

 is in this manner, at least, that he then represented it (PI. III. 

 fig. 4 w.), and he has reproduced the same figure, consequently 

 the same fact, in his large work. 



* Die Iiifusionstliierdien, 1838, p. 362. 



