SPORES AND SPORULATION 21 



spindle-shaped (Fig. 11, c, d), or swollen at one end like a drum-stick 

 (Fig. 11, e,f). The greater part of the cell-contents is withdrawn into this 

 inflated portion, and forms the spore, but some remains in the cylindrical 

 section of the cell, where it can be rendered visible by plasmolysis as an 

 extremely delicate layer lining the membrane. It is no doubt from this 

 remnant of protoplasm that the cilia derive their nourishment at the time of 

 sporulation ; for they are not drawn in during the process, but continue to 

 lash vigorously to and fro until the spore is set free and nothing but the 

 empty cell remains. The spindle-shaped butyric bacilli and the drum-stick 

 cells of some bacteria in bog-water form their spores in this manner, and it 

 seems that in all cases where the spore-bearing part of the cell alters its 

 shape some of the protoplasm remains in the cylindrical section. 



It is certain, in spite of many contradictory statements, that the 

 alteration in shape has the value of a specific character, and can be used 

 for classificatory purposes. The significance of the process lies, of course, 

 not in the change of shape, but in the differentiation of the cell-contents into 

 two parts, one for the maintenance of life in the cell, the other subservient 

 to reproduction. It is a foreshadowing of that division of labour which 

 secures the distribution of spores and their transport to places suitable for 

 germination. 



Endospores are still unknown in a large number of bacteria — in the 

 whole group of cocci, for instance, and in many pathogenic forms, such as the 

 bacteria of typhoid fever, tuberculosis, diphtheria, and cholera. That they 

 do form spores there can be no doubt, but our artificial methods of culture 

 do not offer them the necessary conditions, the determination of which is 

 one of the important tasks that bacteriology has before it. In the patho- 

 genic bacteria mentioned, as well as in many other forms, highly refracting 

 granules have been described as spores, but proof is wanting ; they have not 

 been seen to germinate. It is certain that in a number of cases what have 

 been taken for spores are merely ' chromatin-granules ' and plasmolysed 

 lumps of protoplasm in disintegrated or decaying cells. 



Ordinary methods of staining leave the spores untinged, and they 

 appear, so long as they remain within the body of the cell, as clear colourless 

 spaces. It must be remarked, however, that we are not for this reason 

 justified in regarding all clear spaces in stained bacteria as spores. Many 

 methods have been elaborated for obtaining beautiful double staining of 

 the spores within the rods, the impermeability of the spores being over- 

 come by boiling them in the staining solution, or by submitting them to the 

 action of substances like chromic acid, which render the spore-membrane 

 more penetrable, either by causing it to swell up, or more probably by 

 dissolving out certain constituents. The question whether any given 

 structure is a spore cannot, however, be decided merely by its colour 

 reaction — germination is the only reliable proof. 



