THE BEGINNINGS OF LIFE. 267 



pellicle ' of Pouchet. On microscopical examination of 

 the fluid by the highest powers, as soon as it begins to 

 grow clouded, it will be found swarming with multitudes 

 of mere moving specks or spherical particles, inter- 

 mixed with short staff-like bodies, known as Bacteria, 

 which also exhibit more or less active movements. The 

 specks, that have hitherto been called c Monads 1 } or 

 'microzymes 2 ,' I shall henceforth term plastide-particles. 

 They are primordial particles of living matter, and 

 may be seen, with our present optical powers, to vary 

 between -^-oW" and ^ w " in diameter. 



An examination of the c pellicle,' moreover, shows 

 that it is composed of a dense superficial aggregation 

 of such bodies as may previously have been found 

 diffused through the liquid. In addition to plastide- 

 particles and Bacteria, however, other low organisms, of 



1 Much confusion results from the classifications of the older natu- 

 ralists, who (following O. F. Miiller) arranged under the same genus 

 (Monas) the mere moving specks above referred to, and also certain of 

 the most elementary and smaller of the Ciliated Infusoria of which the 

 so-called Monas lens is about the most abundant representative. It will 

 now be better, in order not to clash with modern usage, to follow the 

 example already set by others, and to restrict the word ' Monad ' to the 

 ciliated organisms which have lately been so well described by Cien- 

 kowski and others. 



2 They were called Microzyma by B^champ, but I do not adopt this 

 designation, because it is too special. All minute living particles, whose 

 nature cannot be distinguished by the microscope, may well be desig- 

 nated by one generally applicable name. Minute off-castings from 

 white blood corpuscles are quite indistinguishable microscopically from 

 the living specks which appear in fermenting solutions, and yet it would 

 not be reasonable to call the former ' small ferments ' (microzymae). 



