60 GENERAL HISTORY OF 



homogeneous and diaphanous, save in the cases where the 

 surface appears reticulated from contraction. 



"The fleshy substance of the Infusoria, isolated by tearing, 

 or by the death of the animalcule, appears in the liquid 

 as lenticular discs or globules, which refract light but 

 slightly, and are capable of forming spontaneously, in their 

 substance, spherical cavities, analagous, in appearance, to 

 the vesicles of the interior. The vesicles formed in the 

 interior of the Infusoria are destitute of a proper mem- 

 brane, and can contract even to so great an extent as to 

 disappear, or many amalgate or incorporate, as it were, 

 together. Some are produced at the base of a sort of 

 mouth, and are destined to contain the water swallowed 

 with the aliments ; they run a long, a certain course, in 

 the interior, and contract and leave nothing in the middle 

 of the fleshy substance except those particles not digested, 

 or they can evacuate their contents externally, by a for- 

 tuitous opening, which may be reproduced several times, 

 although not identical towards the same point, and which 

 may lead to the belief of the presence of an anus. 



" The vesicles containing the aliments are independent, 

 and neither communicate with an intestine nor with each 

 other, save in those cases where two vesicles incorporate 

 together. 



" The other vesicles, which contain nothing but water, 

 are formed much nearer the surface, and appear to be 

 able to receive and expel their contents through the 

 meshes of the tegument. 



" We may consider them, along with Spallanzani, as re- 

 spiratory organs, or at least as intended to multiply the 

 points of contact of the interior substance and the sur- 

 rounding fluids. 



