INFUSORIA. 93 



alimentary system attributed to these creatures by the German 

 physiologist. He laboured to establish the fact that the coloured 

 globules which appeared in the bodies of the Infusoria, while sub- 

 jected to a regimen of carmine and indigo, are not confined by a 

 membrane ; that is to say, they are not contained in special alimen- 

 tary sacs, and that these so-called stomachs are, as stated by Milne- 

 Edwards, " nothing but a species of reservoirs, constituted," as he 

 says, " by the alimentary matter with which each is gorged, united 

 into a rounded pasty mass, so that it could no longer be dispersed, 

 but would continue to advance, still preserving its form. We have, 

 in short, seen these spherules changing their places, and passing one 

 another in their progress from the mouth through the intestinal canal. 

 That they could not do this is evident, if many stomachs were 

 attached to the intestinal canal !" 



This opinion, due to the patient and precise studies of Dujardin, 

 has been adopted by most naturalists of eminence. Besides, this 

 learned rnicroscopist does not admit that there was in the sarcodic 

 mass of Infusoria any pre-existent special alimentary cavity destined 

 to receive the food. In a word, he does not recognise in them any 

 true stomach whatever. This view of the extreme simplicity of 

 structure in the Infusoria has, however, met with opposition even by 

 some recent writers. To accord them neither four nor two stomachs, 

 it is not necessary to deprive them of the organ altogether. Meyen 

 represents them as having one great hollow stomach occupied by a 

 pulpy matter, into which the alimentary masses are successively 

 absorbed. "All recent observations," says Milne-Edwards, "tend to 

 establish the fact that the digestive apparatus of the ciliate Infusoria 

 consists of first, a mouth ; second, of a pharyngeal canal, in which 

 the food often assumes the form of a bolus ; third, of one great 

 stomach with distinct walls, and more or less distant from the com- 

 mon tegumentary membrane ; fourth, of an excretory orifice." 



This mouth presents sensible differences, both as to its position 

 and conformation, often occupying the bottom of a hollow, the edges 

 of which are furnished with well-developed cilia, the action of which 

 attracts the aliment ; in short, the mouth is a sort of decoy at the 

 bottom of a simple pit, being at once contractile and prehensile, the 

 interior part being sometimes capable, according to Milne-Edwards, 

 of being turned inside out in the form of a trumpet, while in a great 

 many species it is provided with a peculiar armature, consisting of a 

 band of rigid bristles disposed in the form of a bow-net, and suscep- 

 tible of dilatation and contraction, according to the wants of the 

 animal. The oesophagus, which is connected with the mouth, has 



