Philosophy of Botany. 271 



We ha\'e here arrived at the limits of our physical investiga- 

 tion. The nature' of light, the properties of the refracting- 

 media, and the structure of the human eye will hardly permit 

 us to penetrate deeper into this special investigation. 



Of the bacteria we know little more than their external 

 form, their reaction ujjon certain coloring substances which 

 render their hyaline bodies visible under the high magnifying 

 powers which we have to use to make them visible. They be- 

 come distinguishable under culture in certain nutritive liquids, 

 through peculiar forms of aggregation, through rapid multipli- 

 cation by division, and through the products of their growth. 

 This growth is due to the absorption of the nutritive fluid, and 

 to the subseciuent elimination of waste material. 



In a state of rest the moners appear as minute globular cor- 

 puscles, either undiscernable to the naked eye, or merely the 

 size of a small pin head, as before stated. Their faculty of exe- 

 cuting movements takes place through the protrusion of irreg- 

 ular fingerlike protuberances from the slimy surface, or of fine 

 radiating filaments or pseudopodia. The pseudopodia are 

 simple, immediate continuations of the structureless albumi- 

 nous mass which constitutes the entire body. We are not 

 able to find in it difl:erentiated parts, and we can make the 

 direct proof for the absolute homogeneity of the semiliquid 

 albmiiinous substance by observing them under the micro- 

 scope in the act of taking food. If minute bodies, acceptable 

 to their tastes, such as comminuted organic substances or in- 

 fusory animals, come into actual contact, they adhere to the 

 sticky surface and create an irritation. In response to this 

 an increased flow of the slimy substance toward that particle 

 takes place, which ultimately incloses it. Sometimes a fun- 

 nel-shaped depression forming in the moner serves the same 

 purpose. The nutriment is thereafter digested by diffusion 

 (endosmosis) and wdiat is left unabsorbed brought to the 

 surface again in a corresponding way. Equally simple is their 

 mode of propagation, which is asexual or by monogamy, and 

 consists simply in self-division. Whenever such a minute 

 body acc^uires a certain size from sufficient nutrition, it parts 

 into two pieces ; an annular constriction forms first, and the 

 division is soon complete. 



