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 relatively 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 physiological function, 

 are known as permanent forms (spores). These may be of two kinds, viz., endo- 

 genous spores, and arthrospores. Any account relative to the continuation of 

 the species will therefore 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 composed 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 endogenous spore or 

 endospore. The greater density of its contents is evidenced 

 by their greater refractive properties, which, were they 

 confined to the spores, would enable these to be detected 

 I m r with certainty by the optical method alone. This is, how- 

 FIG. 14. Bacillus ever, not the case ; large, highly-lustrous drops of a fatty 

 megatherium. nature, and which cannot, without other means, be accu- 



Spore formation. rately identified, occurring frequently in the cell plasma 

 r. chain of four cells o f the fission fungi. In such cases germination tests dealt 



31^ ripl> ' tou h ' with in the following chapter must be resorted to for the 



wauea enaospores. , 



(After De Bary.) purpose of differentiation . 



Magn. 600. With regard to the transformations undergone by the 



individual parts of the contents of the mother- cell prece- 

 dent to spore formation, uncertainty still prevails. According to the observa- 

 tions 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." 



Soon after spore formation has terminated, the membrane of the mother-cell 

 is dissipated, swelling up and dissolving in the surrounding liquid, and thus 

 leaving the spore free. This is the ordinary course, but in many instances 

 deviations occur, one of them being in the case of the Spirillum endoparagogicum, 

 discussed rather more fully below. In this case the membrane of the mother- 

 cell encloses the spore long after the latter is mature, and is still present when 

 the spore germinates. This is described in the next chapter. 



49. Alterations in the Form of the Mother-Cell. 



In many instances the mother-cell undergoes alterations of form during the 

 process of spore formation, and swelling occurs. 



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