658 



FUNGI 



Chains of cocci are found by microscopical examination, and some of 

 the cells in a chain are enlarged without changing their form and 

 develop into typical arthrospores. 



The Bacteria behave very variously under the same conditions 

 of supply or exclusion of oxygen. The aerobic require free oxygen 

 in quantity, as e.g. B. subtilis; while in the anaerobic the vital 

 activities are promoted by its exclusion. But there can be no doubt 

 that gradual modification of either condition will bring about adapta- 

 tions. Naegeli has shown that there are forms which usually depend 

 on oxygen which continue to vegetate when free oxygen ceases. 



FIG. 493. A, Bacterium termo, each cell furnished with a single flagellum. Magni- 

 fied 4,000 diameters. B, C, D, Bacterium lineola, each cell when separated 

 having a flagellum at either end. Magnified 3,000 diameters. (Dallinger.) 



Their nutrition is carried on like that of other vegetative forms 

 devoid of chlorophyll. The actual typical group are without doubt 

 the saprophytic Bacteria. The relation of the parasitic or pathogenic 

 forms to these is one of the most interesting problems in microscopic 

 biology. That they are physiological modifications of the saprophytic 

 forms appears per se a possibility ; but in the light thrown upon 

 biological change and survival by the hypothesis of the origin of 

 species, the suggestion incites to practical inquiry and research. If 

 the parasitic Bacteria are physiological modifications of the saprophytic 

 forms, to know the path by which they biologically became such in.tv 



FIG. 494, Four individuals of Vibrio ntgula, each showing flagellum at one or 

 both ends ; two other individuals, a and b, separating from each other, and draw- 

 ing out a protoplasmic filament to form their second flagella. Magnified 2,000 

 diameters. (Dallinger.) 



be to put more into the hands of medicine than could be accomplished 

 by any other means. 



Bacterium termo is the most universally present and abundant of 

 the saprophytic species. It is Ip to I'Qp. long, and 0'5 to 0'7/i broad, 

 usually of dumbbell form. These Bacteria are usually seen in ' vacil- 

 lating ' movement in their free state ; each cell bears a flagellum at 

 each end, as B, D (fig. 493), whilst the double cells bear a flagellum 

 at each extremity. The formation of the second flagellum takes place 

 by the drawing out of a filament of protoplasm between two cells 

 that are separating from each other (as in fig. 494. , b), the rupture 



