§ III.] Endosporous Bacteria. 15 



III. 



Course of development. Endosporous and Arthro- 

 sporous Bacteria. 



The diflferent conformations and groupings described in the 

 preceding lectures indicate primarily nothing more than de- 

 finite forms of one phenomenon marked in each case by a 

 distinct name, such as present themselves at any moment of 

 observation, and without reference to their origin or future 

 destination. They are forms of the vegetative development, 

 grovrth-forms as they may be shortly termed, and correspond 

 to those which in the higher plants are designated by the words 

 tree, shrub, bulbous plant, and the like. Forms which are 

 determined only by their conformation correspond indeed only 

 to separate members of a particular growth, such as woody 

 stem, tendril, tuber, bulb, &c. 



If we wish to know the significance of a tendril or a bulb in 

 the chain of phenomena, or indeed that of any other form of 

 living creature, we must answer the above questions of its 

 origin and destination, or, to use the customary form of words, 

 we must learn the course of its development. For every form 

 of living being taken at any one moment of time, though it 

 may be present in millions of specimens, is only a member of a 

 chain of periodic movements which coincide with a regular 

 alternation of forms. If therefore we wish for a more intimate 

 acquaintance with Bacteria, we must proceed to enquire into 

 their course of development. 



As far as our present knowledge goes, this development is 

 not quite the same in all cases. We must distinguish two 

 groups, one of which contains the Endosporous, the other the 

 Arthrosporous Bacteria. 



The former group consists of a number of straight rod- 

 forms which will here receive the special name of Bacillus, and 

 a few screw-twisted Spirilla. The phenomena, so far as they 



