THE LIFE HISTORY OF BACTERIA. 53 



rise to two or more spores. All that it can do is to repro- 

 duce the type from which it originally developed. The 

 germinating spore gives rise to one young- cell, and, inasmuch 

 as a fully developed cell produces only one spore and then 

 dies, it follows that spore production or germination is in 

 no wise a means of multiplication. The spore is therefore 

 solely a reproductive or perpetuating form. 



The process of germination of spores is not the same for 

 all species. It will vary, more or less, with different types, 

 but there is reason to believe that it is always constant for 

 a given species. The mode of germination, consequently, 

 might be made use of in classifying- bacteria but, unfortu- 

 nately, it requires a very careful and prolonged observation. 

 For this reason, the study of the germination of spores is 

 very rarely resorted to. The process has been followed out 

 in only a relatively small number of bacteria, probably in 

 not more than 10 or 12 species. 



The first change observed when the spore is about to 

 germinate is that it swells up and lengthens. This increase 

 in size is probably due to imbibition of moisture. As the spore 

 enlarges it becomes less bright. The marked refraction 

 disappears and gives place to a dull appearance. The altered 

 spore now gives rise to a young cell in one of three ways. 



1. Direct germination. The spore gradually changes, 

 by elongating and growing, directly into a new cell. In 

 this case no shell or spore-wall is thrown off, as such, but 

 it may possibly .be softened and dissolved during the pro- 

 cess of conversion. Bearing in mind the development of 

 the spore, as a condensation of the cell protoplasm, it 

 would seem that this method of germination was the 

 reverse of sporulation. It has, however, been observed 

 in but one or two cases (Fig. 14 a). 



Usually the spore-wall splits open at some one place 

 on the surface and through the opening thus produced the 

 young cell makes its appearance. The opening in the 

 spore-wall may be at one or both ends, that is to say polar, 



