154 EVOLUTION OF LIFE. 
the farmer lived in Florida, and would turn his pigs in the 
woods, nature would blindly bring about the same result, 
since the white pigs would soon die, it being well known 
that pigs eat "the paint roots (Lachnanthes , which color 
their bones pink, and which cause the hoofs of all but 
the black varieties to drop off:” hence the squatters say 
“we select the black members of a litter for raising, as they 
" Suppose man to be 
alone have a good chance of living. 
heartless enough to abolish all hospitals, almshouses, etc., 
soon nature would eliminate, as Sparta got rid of, the sickly 
and deformed, the result being the survival of the fittest. 
We have seen that there is a most complex struggle for 
existence, that while like begets like, plants and animals 
vary in their organization ; it follows, necessarily, that those 
organisms whose variations give them an advantage in the 
struggle for existence will survive, or be naturally selected, 
while those not so favored will die out. We see, therefore, 
that Natural Selection neither implies the existence of a 
Natural Selector nor is the Survival of the Fittest effected 
by chance. The facts of Inheritance are to be explained 
by the laws of Generation, those of Variation by Nutrition. 
The Struggle for Existence is caused by the number of 
individuals that are born being out of all proportion to 
the size of the earth they live in. The ever-changing 
conditions of Nature have the effect of eliminating the 
conservative kinds of life, while the plastic organisms sur- 
vive and transmit their peculiarities to posterity. These 
variations become more marked from generation to gener- 
ation, until finally, in the course of ages, there result very 
different forms of plant and animal life. 
A good illustration of this whole subject is the history 
of the Siredon and Amblystoma. The Siredon lichenoides 
(Fig. 65) is a perennial gill-breathing Batrachian reproduc- 
ing Siredons; the Amblystoma mavortium (Fig. 66) breathes 
by lungs and reproduces Amblystomas. These forms were 
