OF MTCRO-ORGANISMS. 43 



other species of higher organization, this mode of ali- 

 mentation is rendered impossible by the cutitcle which 

 encompasses the body; the formation of a cuticle im- 

 pervious to solid foods creates the necessity of a buccal 

 orifice through which food may enter into the interior 

 of the protoplasm. 



A curious graduation in these phenomena is noticed 

 here. Thus there are organisms destitute of a per- 

 manent and pre-existing mouth; their mouth is im- 

 provised as the occasion demands, is adventitions, so 

 to say, and the reason that these organisms are 

 ranked higher than the preceding ones, is that the 

 mouth is invariably formed in the same place. 



In this connection we may examine a small flagel- 

 late Infusory which abounds in impure waters, the 

 Monas vulgaris. It carries a long flagellum attached 

 to its anterior extremity, which when not in motion, is 

 coiled up against the body. At the base of the flagel- 

 lum the protoplasm projects a pellucid substance in 

 the shape of a lip. This protuberance is hollow, 

 containing a vacuole filled with liquid. Cienkotvski 

 has described how these different organs act. The 

 Bacteria and Micrococcus, which constitute the food 

 of the Monas, are. pulled into the latter's neighborhood 

 by strokes of the flagellum; at that instant, the animal 

 becomes conscious of the proximity of these other 

 bodies, for the protuberance which lies at the base of the 

 flagellum extends towards the corpuscule, envelops it 

 in its own substance, and pulls it back into the interior 

 of the Monad's body. Biitschli has made an analo- 

 gous observation with the Oikomonas termo. 



The prehension of food comprehends, here, three 

 phases, in two of which the organism manifests 

 psychical activity : first, attraction of food by means 



