CHAPTER V. 



THE PERMANENT (REPRODUCTIVE) FORMS OR SPORES. 



48. The Formation of the Endospores. 



THE cell forms, hitherto considered, produced by fission, and 

 generally designated vegetative forms of growth, have only rela- 

 tively low powers of resisting the multifarious dangers to which 

 bacteria are exposed in Nature. The fact that, nevertheless, 

 these tender organisms hold their ground is due to their faculty 

 for producing special forms, which, on account of their physio- 

 logical function, are known as permanent forms (spores). These 

 may be of two kinds, viz., endogenous spores, and arthrospores. 

 Any account relative to the continuation of the species will there- 

 fore have first to deal with the formation of the endospores. 



When a bacterial cell commences to develop such a new form, 

 it condenses its cell contents into a smaller 

 space and then surrounds them with a tough, 

 smooth, colourless membrane (probably com- 

 posed of two layers). The form thus produced 

 is enclosed on every side by the membrane 

 of the mother-cell (Fig. 14), in which it is 

 developed, and is therefore called an endo- 

 genous spore or endospore. The greater 

 FIG. 14.- Bacillus density of its contents is evidenced by their 

 megatherium. greater refractive properties, which, were they 



Spore formation. confined to the spores, would enable these 

 r. chain of four ceils with to be detected with certainty by the optical 

 &$$ method alone. This is, however, not the 

 j>eary.)Magn.6oo. case ; large, highly-lustrous drops, of a fatty 

 nature, and which cannot, without other 

 means, be accurately identified, occurring frequently in the cell 

 plasma of the fission fungi. In such cases germination tests 

 dealt with in the following chapter must be resorted to for the 

 purpose of differentiation. 



With regard to the transformations undergone by the indi- 

 vidual parts of the contents of the mother-cell precedent to spore 

 formation, uncertainty still prevails. According to the observations 

 of P. Ernst ( 35), the chromatin granules of the central substance 

 appear to play an important part in these changes, on which 

 account this worker entitled them " sporogenic granules" 



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