452 



PROTOPHYTA 



within the wall of the mother-cell. The mature spore is usually a highly 

 refringent body with definite outline, and of globular or ellipsoidal form. 

 The formation of spores commonly takes place when the substratum 

 yields no more nourishment, or vegetation is otherwise interrupted, and 

 it usually occurs in most of the cells, others remaining sterile. Arthro- 

 sporous reproduction is effected by the simple separation of members 

 which form the starting point of new growths. 



The spores of Bacteria are capable of germination from maturity 

 onwards, often for considerable periods. They withstand the operation 



of external agencies, such as ex- 

 treme degrees of temperature and 

 the like, with varying success, many 

 of them exhibiting astonishing en- 

 durance. Such arthrosporous forms 

 as Beggiatoa, which vegetate in 

 water, are probably incapable of 

 withstanding desiccation at a very 

 high temperature, but the spores 

 of endosporous Bacteria possess, 

 many of them, remarkable powers 

 of endurance. The spores of Ba- 

 cillus Anthracis (Cohn) (the cause 

 of splenic fever) remain alive in 

 absolute alcohol. They may be 

 kept for at least three years in an 

 air-dry state, and for at least one 

 year in water, and probably for 

 longer either in air or in water. 

 They were found by Brefeld to with- 

 stand boihnginanutrientsolutionfor 

 a quarter of an hour, the greater part 

 of them for half an hour, a smaller 

 number for one hour, but none 

 for three hours. And so with the 

 spores of other forms. The tempe- 

 ratures at which germination takes 

 place, the minimum, the optimum, and the maximum, vary with different 

 forms ; but for the most part the minimum and certainly the optimum 

 may be said to be above the ordinary temperature of a room. Similarly 

 the optimum temperature for vegetation is usually high, being about 

 3o°C., speaking very generally. 



With reference to their behaviour towards the supply or exclusion of 



By. a, 

 , a pair of 



Fig. 380. — Bacillus Mega-terunii de 

 outline of a motile chain of rods \ by 

 same ; /, a quadricellutar rod after treatment 

 with alcoholic solution of iodine ; c, a five- 

 celled rod before spore-formation ; d—f^ suc- 

 cessive stages of pair of rods while forming 

 spores, about an hour interval between each — 

 state d was about two o'clock afternoon, and 

 the spores in y were ripe towards evening ; r, 

 a quadricellular rod with ripe spores ; g^ a 

 five-celled rod with three ripe spores placed 

 in a nutrient solution after several days' desic- 

 cation at 12.30 ; g-y same about 1.30 ; g^^ the 

 same about 4 o clock; A", two spores with 

 the walls of the mother-cells dried, and then 

 placed in a nutrient solution about 11.45 \ ^'"» 

 the same about 12.30; z, k, I, later stages of 

 germination ; m, a rod formed fi-om a spore 

 placed eight hours before in a nutrient fluid, 

 and in the act of splitting transversely, {a x 

 250, the other figures x 600.) f.\fter de Barj'.) 



