26 COMPARATIVE ZOOLOGY. 
the young shoot rises above the soil, and unfolds itself to 
the light of the sun, at the touch of whose mystic rays 
chlorophyl is created, does real, constructive vegetation 
begin; then its mode of life is reversed — carbon is re- 
tained and oxygen set free. 
Most plants, and many animals, multiply by budding 
and division; on both we practice grafting; in both the 
cycle of life comes round again to the ovule or ovum. 
Do annuals flower but to die? Insects lay their eggs in 
their old age. But in all cases of true ovulation, the ani- 
mal embryo absorbs its yolk from the inside, while that of 
a seed is itself surrounded by the albumen. 
Animals generally possess sensation, consciousness, and 
volition. Yet volition is wanting in some lower forms; 
and many plants show excitability, if not sensibility. For 
aught we know, irritability is the birthright of all living 
matter. In plants, the protoplasm is scattered and buried 
in rigid structures: feeling is, therefore, dull. In animals, 
the protoplasm is concentrated into special organs, and so 
feeling, like electricity rammed into Leyden jars, goes off 
with a flash." 
The self-motion of animals and the rooted state of plants 
is a very general distinction; but it fails where we need it 
most. It is a characteristic of living things to move. The 
protoplasm of all organisms is unceasingly active.” Be- 
sides this internal movement, myriads of plants, as well 
as animals, are locomotive. Rambling Diatoms, writhing 
Oscillaria, and the agile spores of Cryptogams crowd our 
waters, their instruments of motion (cilia) being of the 
very same character as in microscopic animals; while 
Sponges, Corals, Oysters, and Barnacles are stationary. 
A contractile vesicle is not exclusively an animal prop- 
erty, for the fresh-water Volvox and Gonium have it. 
The act of muscular contraction in the highest animal is 
due to the same kind of change in the form of the cells of 
