REPRODUCTION. 
191 
CHAPTER XIX. 
REPRODUCTION. 
It is a fundamental truth that every living organism 
has had its origin in some pre-existing organism. The 
doctrine of “spontaneous generation,” or the supposed 
origination of organized structures out of inorganic parti¬ 
cles, or out of dead organic matter, has not yet been sus¬ 
tained by facts. 
Reproduction is of two kinds — sexual and asexual . 
All animals, probably, have the first method, while a very 
great number of the 
lower forms of life have 
the latter also. 
Of asexual reproduc¬ 
tion there are two kinds 
— Self - division and 
Budding . 
Self-division, the 
simplest mode possible, 
is a natural breaking-up 
of the body into distinct 
surviving parts. This 
process is sometimes ex¬ 
traordinarily rapid, the 
increase of one animal¬ 
cule (Paramoecium) be¬ 
ing; computed at 268 Flo. 160.—Reproduction of Infusoria (VorticeU 
® , Ice and others) by fission or self-division. 
millions in a month. It 
may be either transverse or longitudinal . Of the first 
sort,Figs. 1,2,and 3 (Fig. 160) are examples; of the latter, 
