48 MORPHOLOGY 



the cell wall of the mother cell ruptures and liberates the 

 spore surrounded by a newly secreted and highly resistant 

 membrane. The rest of the original cell undergoes disinte- 

 gration. When a spore develops into a vegetative form it 

 usually increases in size, loses its high refractive power, 

 and ruptures. The spore may rupture at the end and form 

 a small pore or opening. From this opening the protoplasm 

 grows out and forms the characteristic bacillus or spirillum. 

 The old spore membrane can be often discerned attached to 

 the new vegetative form. Occasionally the spore membrane 

 splits longitudinally and sometimes transversely, so that the 

 young cell has part of the spore on either end or on both sides 

 of it for a short period as it grows in length. In a few species 

 of bacteria there is no rupture of the spore membrane, it being 

 absorbed by the developing vegetative cell. It is probable 

 that the bacterial cell goes into the spore stage as a means of 

 carrying the cell through unfavorable conditions to a time 

 when normal conditions will be present and the cell can re- 

 produce. Some hold the view that sporulation is the highest 

 stage of the life history of certain bacteria. It is necessary 

 for these bacteria to pass through this stage in order to main- 

 tain a vigorous species. This condition of affairs has been 

 noted among certain of the algae. Others believe that it is 

 always necessary for a bacterium to be placed in unfavorable 

 surroundings to form spores. Yet at certain temperatures 

 which are favorable for bacterial growth sporulation occurs. 

 It is possible that the environment may be rapidly changed 



