22 Lectures on Bacteria. [^ in. 



separate into daughter-rods, that the latter straighten themselves 

 out. 



Endogenous spore-formation, as it has now been described, 

 that is, formation of spores taking place inside the previously 

 vegetative cell, sharply distinguishes the endosporous forms from 

 the rest of the Bacteria, which we have termed arthrosporous. 

 The name is intended to indicate the fact, that in these forms 

 members of an aggregation or of a series of united generations 

 of vegetative cells separating from the rest assume the character 

 of spores immediately without previous endogenous rejuvenes- 

 cence, that is, they may become the origins of new vegetative 

 generations. In a number of the forms comprised in this divi- 

 sion, a more or less distinct morphological difference may be 

 observed between vegetative cells and spores; in others, as 

 far as we know at present, no such distinction is to be found. 



Simple examples of the former kind are supplied by Leuco- 

 nostoc mentioned above and by Bacterium Zopfii, Kurth. The 

 former (Fig. 3) consists, according to van Tieghem's descrip- 

 tion, of curved bead-like rows of small round cells with firm 

 gelatinous coats united together in large numbers into Zoogloeae 

 (Fig. 3, a, b). A large portion of the cells dies at the end of the 

 vegetative period when the nutrient substratum is exhausted. On 

 the other hand single cells irregularly distributed in the rows 

 become somewhat larger than the rest, acquire a more distinct 

 outline, that is, become thicker-walled, and their protoplasm 

 grows darker (Fig. 3, c). They at length become free by the 

 deliquescence of the gelatinous envelopes, and may claim the 

 name of spores, because when placed in a fresh nutrient solution 

 they develope into new rows of beads like those of the mother- 

 plant (Fig. 3, d-h). 



Bacterium Zopfii was originally found by Kurth in the intes- 

 tinal canal of fowls, and then cultivated partly in gelatine partly 

 in suitable watery solutions. In the fresh substratum the Bac- 

 terium vegetates at first in the rod-form. In the gelatine the 

 rods continue united together into large filaments often twisted 



