1 8 Lectures on Bacteria. [$ in. 



begins to be formed is marked by the absence of granulose. 

 This spot looks in solution of iodine like a notch of a pale 

 yellowish colour, occupying one extremity of the rod which 

 elsewhere tends to be blue, and is moreover distinguished by 

 its lower power of refraction even before the use of a reagent. 

 As the spore grows in size the granulose disappears. Accord- 

 ing to Prazmowski the granulose is not always present before 

 the formation of the spore, even in Bacillus Amylobacter. In 

 other Bacilli, the three, for example, just previously named, it 

 has never been observed ; their protoplasm either remains un- 

 changed before spore-formation, or at most becomes a little 

 less transparent and in larger forms more evidently finely 

 granular. 



A mother-cell, so far as can be positively stated, never pro- 

 duces more than a single spore. This can be determined with 

 certainty in almost all cases, and the few accounts which have 

 been given of the formation of two spores in a single cell are 

 doubtful, being unaccompanied by any guarantee that the 

 boundaries of adjoining cells have not been overlooked or 

 errors of other kinds admitted. I must, however, add that an 

 exception to the prevailing rule has recently come under my 

 own observation in the case of a species nearly allied to Bacillus 

 Amylobacter (see Lecture IX), which usually follows the rule, 

 but does also sometimes contain two spores in a cell which has 

 swollen and become broadly fusiform. I have not yet succeeded 

 in observing the further development of the twin spores. 



In cultures formation of spores usually takes place when 

 other growth comes to an end because the substratum is no 

 longer adapted to maintain it, being either exhausted, as we 

 are in the habit of saying, or impregnated with the products 

 of decomposition which are unfavourable to vegetative develop- 

 ment. Formation of spores then spreads rapidly through the 

 larger number of the cells and through the special aggregations, 

 if the particular form is present in abundance. Some of these 

 it is true do not produce spores, in some the process begins 



