MEDIA, TEMPERATURE, AND OXYGEN. 51 



endogenous spores are known only in Sarcina pulmonum, 

 and the strange Spirillum endoparagogicum. l 



As H. Buchner (C. B. vnr, 1) pointed out, sporulation 

 occurs in suitable varieties when the nutrient medium be- 

 gins to be exhausted, therefore most rapidly on nutrient 

 media very poor in nutrient materials. 



On the contrary, a good nutrient medium not only 

 favors the growth of bacilli but also the formation of spores, 

 in so far as the vigorously growing bacilli also luxuriantly 

 and regularly sporulate (K. B. Lehmann and Osborne, A. 

 H. xi, 51); see especially also Stephanidis (A. H. xxxv, 1). 

 The crop of spores is exceedingly large. The quality (resist- 

 ance) of spores which are grown upon various nutrient 

 media was not found by Stephanidis to vary. For many 

 details consult Schreiber (C. B. xx, 353). 



For sporulation a higher temperature is sometimes 

 (always?) required than for the vegetative growth. The 

 anthrax bacillus, for example, thrives at 13 to 14, but 

 does not form spores below 18. 



All aerobic bacteria require, especially for spore-forma- 

 tion, the presence of oxygen ; how the facultative anae- 

 robes conduct themselves in this respect is still to be 

 learned. 



Obligate anaerobes only produce spores if oxygen is 

 excluded or, with the admission of oxygen, in mixed cul- 

 tures or in association with dead synergetic bacteria. 



Spores never germinate in media in which they have 

 developed when they have been exhausted or rendered 

 detrimental by metabolic products. Only after transfer- 

 ring to fresh nutrient media does germination occur, ap- 

 pearing in one or more hours, and having the morphologic 

 peculiarities described on page 26. 



Against all injuries spores are substantially more re- 



J As it is important for our classification, we have carefully sought, 

 in a number of varieties generally considered as being free from spores, 

 to obtain spores as had been done by Migula (Sys. I, 207) by means 

 of quince and marshmallow decoction. We never obtained a perfectly 

 undoubted result. With Bacterium janthinum alone we saw detached 

 pictures, which could be interpreted as spores, but we have not studied 

 their germination. Upon the common nutrient media we have not 

 once seen sporulation in a variety commonly known as not possessing 

 spores. 



