32 OUTLINES OF BACTERIOLOGY 



very probably becomes the membrane of the new vegetative cell, 

 though the latter fact has not been demonstrated. Germination can 

 be very easily observed in the case of those rod-shaped forms which 

 sporulate freely on nutrient agar. The method adopted for obser- 

 vation is as follows : The material is added very thickly to a drop 

 of sterile water, then heated for two minutes at 100 C. to kill off 

 all the vegetative cells, and then sown very plentifully on the 

 surface of an agar-slope. The inoculated tube after being placed 

 in an incubator (28-32 C.) for about six hours, is taken out and 

 microscopically examined. It is advisable to stain with weak 

 fuchsin. The first process consists of a swelling of the spore, with 

 a concomitant loss of its bright glistening appearance. This is 

 evidently the result of absorption of water from the surrounding 

 medium. Then follows a split in the extine through which the 

 young cell protrudes by elongation. This protrusion can be effected 

 in three distinct ways : 



(1) POLAR. When it emerges from one of the poles (Fig. 49a). 



(2) Bi-PoLAR. When it emerges from both the poles (Fig. 495). 



(3) EQUATORIAL. When it emerges from the middle of the spore 



(Fig. 49.). 



Examples of polar germination are seen in Bac. graveolens, Bac. 

 Ellenbachensis, Bac. mycoides, etc.; of equatorial germination, in Bac. 

 subtilis, Bac. hirtus, Bac. petasites, etc.; and of bi-polar germination 

 in Bac. simplex, Bac. cohaerens, etc. Some bacilli germinate in two 

 of these ways, e.g. Bac. cohaerens is at first polar in its germination, 

 then at a later stage the germinating cell may also break out at 

 the other pole, and so become bi-polar. The spores of Bac. subtilis 

 have a further peculiarity in that they occasionally burst the spore 

 membrane right round, so that the halves separate and the young 

 vegetative cell carries a bit of the spore membrane at each end 

 (Fig. 4Sd). The time required for germination varies according to 

 the medium. Prazmowski records 3-4J hours at 30-35 C. for Bac. 

 subtilis. This is doubtless correct for the majority of species, because, 

 if the culture be examined six hours after sowing, it is usual to find 

 a large number of germinated spores, showing that the first spore 

 must have germinated at least a couple of hours sooner. 



Conidia- and Gonidia-Formation. Among the higher bacteria 

 (Chlamydobacteriaceae) the formation of endospores is unknown, but 

 instead, other kinds of spores are formed. There are two kinds, 

 called respectively conidia and gonidia. Both differ from endospores 

 in being less resistant, in being produced in far greater numbers, 



