1890.] The Persistence of Plant and Animal Life. 517 
THE PERSISTENCE OF PLANT AND ANIMAL LIFE 
UNDER CHANGING CONDITIONS OF 
ENVIRONMENT. 
BY PERSIFOR FRAZER. 
|B pial: in the Introduction to his Manual of Geology (1874), 
thus distinguishes between the Plant and Animal Kingdom, 
on the one hand, and the Crystal Kingdom on the other hand: 
“ The plant or animal, (1) endowed with life, (2) commences 
from a germ, (3) grows by means of imbibed nutriment, and (4) 
passes through a series of changes and gradual development to 
the adult state, when (5) it evolves new seeds or germs, and (6) 
afterwards continues on to death and dissolution. It has, hence, 
its cycle of growth and reproduction, and cycle follows cycle in 
indefinite continuance. 
“ The crystal is (1) a lifeless object, and has a simpler history ; 
it (2) begins in a nucleal molecule or particle ; (3) it enlarges by 
external addition or accretion alone, and (4) there is hence no 
proper development, as the crystal is perfect, however minute ; (5) 
it ends in simply existing, and not in reproducing ; and (6) being 
lifeless, there is no proper death or necessary dissolution.” 
In pursuing the subject more in detail this author states of both 
plants and animals that they “ have the fundamental element of 
their structure, visible cells, containing fluid or plastic material, 
instead of invisible molecules.” 
As to this it may be said that while there are some reasons for 
believing, with our present knowledge of the nature of light, that 
the microscope will never reveal to us a single molecule, such a 
revelation is not at all impossible when one considers the gigantic 
strides which have been made in subduing the phenomena of na- 
ture to aid us in penetrating her secrets; but even if it be true 
that we shall never see a single molecule, it is not yet proven that 
a single molecule forms the unit of mineral building. . There’are 
1 An address delivered before the Pennsylvania Horticultural Society, May 20, 1890. 
Am, Nat.—June.—2. 


