myriad voices, to the ice-fields of polar latitudes and those si 
the leading aspects of biological science, and to indicate the direc- 
grand and solemn import, for it embraces man himself and is the 
it is life, and life stretches back into the illimitable past, a 
42 ASPECT OF BIOLOGY AND METHOD OF BIOLOGICAL STUDY. 
Accepting, then, the doctrine of evolution in all freedom andin — 
all its legitimate consequences, there remains, I say, a great resid- 
uum unexplained by physical theories. Natural Selection, the 
Struggle for Existence, the Survival of the Fittest, will’ explain 
much, but they will not explain all. They may offer a beautiful q 
and convincing theory of the present order and fitness of the or- 
ganic universe, as the laws of attraction do of the inorganic, but 
the properties with which the primordial protoplasm is endowed— ~ 
its heredity and its adaptivity—remain unexplained by them, for ~ 
these properties are their cause and not their effect. a 
For the cause of this cause we have sought in vain among the 
physical forces which surround us, until we are at last compelled — 
to rest upon an independent volition, a far-seeing intelligent de- ~ 
sign. Science may yet discover even among the laws of physics 
the cause. it looks for; it may be that even now we have glimpses — 
of it; that those forces among which recent physical research has — 
demonstrated so grand a unity—light, heat, electricity, magnet- ~ 
ism—when manifesting themselves through the organizing proto- 
plasm, become converted into the phenomena of life, and that the : 
poet has unconsciously enunciated a great scientific truth when he — 
tells us of . | 
“ Gay lizards glittering on the walls 
Of ruined shrines, busy and bright 
As though tk alive with light.” 
But all this is only carrying us one step back in the grand gen 
eralization. All science is but the intercalation of causes, each 
tions which biological studies must take. Our science is one 0 
exponent of the laws which he must obey. Its subject is vast, 
forward into the illimitable future. Life, too, is everywhere 
Over all this wide earth of ours, from the equator to the poles, 
there is scarcely a spot which has not its animal or its vegetable den: 
izens—dwellers on the mountain and on the plain, in the lake and 
on the prairie, in the arid desert and the swampy fen; from th 
tropical forest with its strange forms and gorgeous colors and 
