12 BACTERIOLOGY 



refracting, nearly water free, protoplasm, surrounded by a thick 

 tough membrane, which, according to Burchard, is composed of 

 two layers, an inner darker and denser portion and an outer 

 bright delicate layer. The membrane is not equally thick 

 throughout, but in the greater number of species, according to 

 Migula, is thinnest at the poles, although in a number of species 

 the polar portions of the membrane are thickened, and the equa- 

 torial portions thin. Since in germination the thinner portions 

 constitute the locus minoris resistcntice, the structure of the spore 

 wall will determine the character of the germination, as will be 

 explained in the next paragraph. 



Spore Germination. Under favorable conditions of environ- 

 ment spores germinate and develop into vegetative forms. The 

 method of germination varies in different species and groups of 

 species, a point which is likely to have considerable taxonomic 

 value. The first requisite of spore germination is the presence 

 of moisture. It has been stated that the protoplasm of the 

 spores is nearly or quite water free, but it is a common property 

 of all protoplasm to absorb water, which causes it to swell. 

 Thus the first process in spore germination is the enlargement 

 of the spore to double its former dimensions. The tension thus 

 produced causes the rupture of the wall of the spore at its thin- 

 nest portion, be this at one or both poles or at the equator. 

 With the rupture of the wall comes the protrusion of its contents 

 in the form of what may be called the germinal rod. 



The methods of spore germination may be designated as 



follows : 



i. Polar germination. 



2. Equatorial germination. 



3. Germination by absorption. 



4. Endo-germination. 



Polar germination has been illustrated by Prazmowski in 

 Clostridium butyricum, and by Klein in Bact. sessile. Here the 



