76 LIFE. 



arranged so as to form an investing membrane closed at all 

 points, the other lying within, soft, and exhibiting no form 

 or structure whatever. Now if these bodies be placed 

 under favourable conditions certain changes will occur. 

 Let them be put, for instance, upon the moist surface of a 

 glass slide, and after a time let the slide be placed under 

 the microscope. First of all the particles absorb moisture, 

 and swell up, and the membrane becomes thinner in pro- 

 portion to the whole mass, and the matter within increases 

 in amount. 



Next a new change is observed at one point in the 

 membrane. A small orifice is seen, through which a little 

 of the granular contents of the body, covered with a thin 

 layer of the inner part of the membrane, makes its way, and 

 thus a small nodule is formed which projects through the 

 external membrane. By degrees this assumes a structure 

 resembling that of the body from which it has proceeded ; 

 it increases in size; the membrane around it becomes 

 thicker; its point of attachment becomes less and less, until 

 at last it is completely separated, and becomes a free and 

 independent particle, exactly resembling that from which it 

 sprung, except that it is smaller, and capable of growing and 

 giving rise to new individuals like itself, by a repetition of the 

 process by which it was formed. 



This is one way in which the particles may multiply, 

 but there are others. In one of these, too, an orifice forms 

 in the membrane of the particle of mildew, and a little of 

 the soft transparent material escapes, but it does not separate 

 as in the first case ; it remains in connexion with the mass, 

 and grows out into a narrow thread-like process. The mem- 



