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n the way of accepting it to the full extent which has been some- 
times claimed for it. It must be borne in mind that though 
among some of the higher vertebrata we can trace back for some 
distance in geological time a continuous series of forms which may 
safely be regarded as derived from one another by gradual modi- 
fication—as has been done, for example, so successfully by Prof. 
Huxley in the case of the horse—yet the instances are very few 
in which such a sequence has been actually established ; while 
the first. appearance in the earth’s crust of the various classes 
presents itself in forms which by no means belong to the lowest 
or most generalised of their living representatives. On this last 
fact, however, I do not lay much stress, for it will admit of ex- 
planation by referring it to the deficiency of the geological record, 
and then demanding a lapse of time—of enormous length, it is 
true—during which the necessary modifications would be in pro- 
gress before the earliest phase of which we have any knowledge 
could have been reached. 
Again, we must not lose sight of the hypothetical nature of 
those primordial forms in which we regard the branches of our 
genealogical tree as taking their origin ; and while the doctrine 
of the recapitulation of ancestral forms has much probability, 
and harmonises with the other aspects of the Evolution doctrine 
into a beautifully symmetrical system, it is one for which a suffi- 
cient number of actually observed facts has not yet been adduced 
to remove it altogether from the region of hypothesis. 
Even the case of the graptolites already adduced is an illus- 
tration rather than a proof, for the difficulty of determining the 
true nature of such obscure fossils is so great that we may be 
altogether mistaken in our views of their structure and affinities. 
To me, however, one of the chief difficulties in the way of 
the doctrine of Evolution, when carried out to the extreme 
length for which some of its advocates contend, appears to 
be the unbroken ccntinuity of inherited life which it neces- 
” sarily requires through a period of time whose vastness is such 
that the mind of man is utterly incapable of comprehending it. 
Vast periods, it is true, are necessary in order to render the phe- 
nomena of Evolution possible ; but the vastness which the an- 
tiquity of life, as shown by its remains in the oldest fossiliferous 
strata, requires us to give to these periods may be even greater 
than is compatible with continuity. ; 
We have no reason to suppose that the reproductive faculty in 
organised beings is endowed with unlimited power of extension, 
and yet to go no farther back than the Silurian period—though 
the seas which bore the Eozoon were probably as far anterior to 
those of the Silurian as these are anterior to our own—the hypo- 
thesis of Evolution requires that in that same Silurian period the 
ancestors of the present living forms must have existed, and that 
their life had continued by inheritance through all the ramifica- 
tions of a single genealogical tree down to our own time ; the 
branches of the tree, it is true, here and there falling away, with 
the extinction of whole genera and families and tribes, but still 
some always remaining to carry on the life of the base through a 
period of time to all intents and purposes infinite. It is true 
that in a few cases a continuous series of forms regularly passing 
from lower to higher degrees of specialisation, and very probably 
connected to another by direct descent, may be followed through 
long geological periods, as for example, the graduated series 
already alluded to, which may be traced between certain mam- 
mals of the Eocene and others living in our own time, as well 
as the very low forms which have come down to us apparently 
unmodified from the epoch of the Chalk. But incalculably great 
as are these periods, they are but as the swing of the pendulum 
in the Millennium, when compared to the time which has elapsed 
since the first animalisation of our globe. 
Is the faculty of reproduction so wonderfully tenacious as all 
this, that through periods of inconceivable duration, and exposed 
to influences the most intense and the most varied, it has still 
come down to us in an unbroken stream? Have the strongest 
which had survived in the struggle for existence necessarily 
handed down to the strongest which should follow them the 
power of continuing as a perpetual heirloom the life which they 
had themselves inherited? Or have there been many total ex- 
tinctions and many renewals of life—a succession of genealogical 
trees, the earlier ones becoming old and decayed, and dying out, 
and their place taken by new ones which haye no kinship with 
the others? Or, finally, is the doctrine of Evolution only a 
working hypothesis which, like an algebraic fiction, may yet be 
of inestimable value as an instrument of research? For as the 
higher calculus becomes to the physical inquirer a power by 
which he unfolds the laws of the inorganic world, so may the 
parade 0h hs, Gao, 
NATURE 
~~ > a ed 4 A OA Sy Se 
425 
hypothesis of Evolution, though only a hypothesis, furnish the 
biologist with a key to the order and hidden forces of the 
world of life. And what Leibnitz and Newton and Hamilton 
have been to the physicist, is it not that which Darwin has been 
to the biologist ? 
But even accepting as a great truth the doctrine of Evolution, 
let us not attribute to it more than itcan justly claim. No valid 
evidence has yet been adduced to lead us to believe that in- 
organic matter has become transformed into living, otherwise 
than through the agency of a pre-existing organism, and there 
remains a residual phenomenon still entirely unaccounted for. 
No physical hypothesis founded on any indisputable fact has yet 
explained the origin of the primordial protoplasm, and, above 
= of its marvellous properties which render Evolution pos- 
sible. 
Accepting, then, the doctrine of Evolution in all freedom and 
in all its legitimate consequences, there remains, I say, a great 
residuum 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 and convincing theory of the present order and fitness 
of the organic universe, as the laws of attraction do of the in- 
organic, but the properties with which the primordial proto- 
plasm is endowed—its heredity and its adaptivity—remain un- 
explained by them, for these properties are their cause and not 
their effect. 
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 
design. 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, Magnetism—when manifesting themselves 
through the organising protoplasm, become converted into the 
phenomena of life, and that the poet has unconsciously enun- 
ciated a great scientific truth when he tells us of 
“ Gay lizards glittering on the walls 
Of ruined shrines, busy and bright 
As though they were alive with light.” 
But all this is only carrying us one step back in the grand 
generalisation. All science is but the intercalation of causes, 
each more comprehensive than that which it endeavours to 
explain, between the great primal cause and the ultimate 
effect. 
I have thus endeavoured to sketch for you in a few broad 
outlines the leading aspects of biological science, and to indicate 
the directions which biological studies must take, Our science 
is one of grand and solemn import, for it embraces man himself 
and is the exponent of the laws which he must obey. Its subject 
is vast, for it is Life, and Life stretches back into the illimitable 
past, and forward into the illimitable future. Life, too, is every- 
where. Over ail this wide earth of ours, from the equator to the 
poles, there is scarcely a spot which has not its animal or its 
vegetable denizens—dwellers on the mountain and on the plain, 
in the lake and on the prairie, in the arid desert and the swampy 
fen ; from the tropical forest with its strange forms and gorgeous 
colours, and myriad voices, to the ice-fields of polar latitudes 
and those silent seas which lie beneath them, where living things 
unknown to warmer climes congregate in unimaginable multi- 
tudes. There is life all over the solid earth; there is life 
throughout the vast ocean, from its surface down to its great 
depths, deeper still than the lead of sounding-line has 
reached. 
And it is with these living hosts, unbounded in their variety, 
infinite in their numbers, that the student of biology must make 
himself acquainted. It is no light task which lies before him 
—-no mere pastime on which he may enter with trivial purpose, 
as though it were but the amusement of an hour ; it isa great and 
solemn mission to which he must devote himself with earnest 
mind and with loving heart, remembering the noble words of 
Bacon :— 
“ Knowledge is not a couch whereon to rest a searching and 
restless spirit ; nor a terrace for a wandering and variable mind 
to walk up and down with a fair prospect ; nor a tower of state 
for a proud mind to raise itself upon ; nor a fort or commanding- 
ground for strife and contention ; nor a shop for profit and sale ; 
but a rich storehouse for the glory of the Creator, and the relief 
of man’s estate.” 
