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CHAP. XXI.

ALTERNATE GENERATION.

421

externally, no visible departure from the normal form. Thus, in one region a species may possess peculiar medicinal qualities which it wants in another, or it may be hardier and better able to resist cold. The average range in altitude, says Hooker, of each species of flowering plant in the Himalayan Mountains, whether in the tropical, temperate, or Alpine region, is 4,000 feet, which is equivalent to twelve degrees of isothermals of latitude. If an individual of any of these species be taken from the upper limits of its range and carried to England, it is found to be better able to stand our climate than those from the lower or warmer stations. When several of these internal or physiological modifications are accompanied by variation in size, habits of growth, colour of the flowers, and other external characters, and these are found to be constant in successive generations, botanists may well begin to differ in opinion as to whether they ought to regard them as distinct species or not.

Alternate Generation.

Hitherto, no rival hypothesis has been proposed as a substitute for the doctrine of transmutation; for what we term 'independent creation,' or the direct intervention of the Supreme Cause, must simply be considered as an avowal that we deem the question to lie beyond the domain of science.

The discovery by Steenstrup of alternate generation enlarges our views of the range of metamorphosis through which a species may pass, so that some of its stages (as when a Sertularia and a Medusa interchange) deviate so far from others as to have been referred by able zoologists to distinct genera, or even families. But in all these cases the organism, after running through a certain cycle of change, returns to the exact point from which it set out, and no new form or species is thereby introduced into the world. The only secondary

422

INDEPENDENT CREATION.

CHAP. XXI.

cause, therefore, which has, as yet, been even conjecturally brought forward, to explain how, in the ordinary course of nature, a new specific form may be generated is, as Lamarck declared, variation,' and this has been rendered a far more probable hypothesis by the way in which Natural Selection is shown to give intensity and permanency to certain varieties.

Independent Creation.

When I formerly advocated the doctrine that species were primordial creations, and not derivative, I endeavoured to explain the manner of their geographical distribution, and the affinity of living forms to the fossil types nearest akin to them in the tertiary strata of the same part of the globe, by supposing that the creative power, which originally adapts certain types to aquatic and others to terrestrial conditions, has, at successive geological epochs introduced new forms best suited to each area and climate, so as to fill the places of those which may have died out.

In that case, although the new species would differ from the old (for these would not be revived, having been already proved by the fact of their extinction, to be incapable of holding their ground), still, they would resemble their predecessors generically. For, as Mr. Darwin states in regard to new races, those of a dominant type inherit the advantages which made their parent species flourish in the same country, and they likewise partake in those general advantages which made the genus to which the parent species belonged, a large genus in its own country.

We might, therefore, by parity of reasoning, have anticipated that the creative power, adapting the new types to the new combination of organic and inorganic conditions of a given region, such as its soil, climate, and inhabitants, would introduce new modifications of the old types,-marsupials,

CHAP. XXI.

INDEPENDENT CREATION.

423

for example in Australia, new sloths and armadilloes in South America, new heaths at the Cape, new roses in the northern, and new calceolarias in the southern hemisphere. But to this line of argument Mr. Darwin and Dr. Hooker reply, that when animals or plants migrate into new countries, whether assisted by man, or without his aid, the most successful colonisers appertain by no means to those types which are most allied to the old indigenous species. On the contrary, it more frequently happens that members of genera, orders, or even classes, distinct and foreign to the invaded country, make their way most rapidly, and become dominant at the expense of the endemic species. Such is the case with the placental quadrupeds in Australia, and with horses and many foreign plants in the pampas of South America, and numberless instances in the United States and elsewhere, which might easily be enumerated. Hence, the transmutationists infer that, the reason why these foreign types, so peculiarly fitted for these regions have never before been developed there, is simply that they were excluded by natural barriers. But these barriers of sea, or desert, or mountain, could never have been of the least avail, had the creative force acted independently of material laws, or had it not pleased the Author of Nature that the origin of new species should be governed by some secondary causes analogous to those which. we see preside over the appearance of new varieties, which never appear except as the offspring of a parent stock very closely resembling them.

424

THEORY OF TRANSMUTATION.

CHAP. XXII.

CHAPTER XXII.

OBJECTIONS TO THE HYPOTHESIS OF TRANSMUTATION CONSIDERED.

STATEMENT OF OBJECTIONS TO THE HYPOTHESIS OF TRANSMUTATION FOUNDED ON THE ABSENCE OF INTERMEDIATE FORMS-GENERA OF WHICH, THE SPECIES ARE CLOSELY ALLIED —OCCASIONAL DISCOVERY OF THE MISSING LINKS IN A FOSSIL STATE-DAVIDSON'S MONOGRAPH ON THE BRACHIOPODA WHY THE GRADATIONAL FORMS, WHEN FOUND, ARE NOT ACCEPTED AS EVIDENCE OF TRANSMUTATION-GAPS CAUSED BY EXTINCTION OF RACES AND SPECIES-VAST TERTIARY PERIODS DURING WHICH THIS EXTINCTION HAS BEEN GOING ON IN THE FAUNA AND FLORA NOW EXISTING GENEALOGICAL BOND BETWEEN MIOCENE AND RECENT PLANTS AND INSECTS-FOSSILS OF OENINGHEN-SPECIES OF INSECTS IN BRITAIN AND NORTH AMERICA REPRESENTED BY DISTINCT VARIETIES- FALCONER'S MONOGRAPH ON LIVING AND FOSSIL ELEPHANTS-FOSSIL SPECIES AND GENERA OF THE HORSE TRIBE IN NORTH AND SOUTH AMERICA-RELATION OF THE PLIOCENE MAMMALIA OF NORTH AMERICA, ASIA, AND EUROPE-SPECIES OF MAMMALIA, THOUGH LESS PERSISTENT THAN THE MOLLUSCA, CHANGE SLOWLYARGUMENTS FOR AND AGAINST TRANSMUTATION DERIVED FROM THE ABSENCE OF MAMMALIA IN ISLANDS-IMPERFECTION OF THE GEOLOGICAL RECORD-INTERCALATION OF NEWLY DISCOVERED FORMATION OF INTERMEDIATE AGE IN THE CHRONOLOGICAL SERIES-REFERENCE OF THE ST. CASSIAN BEDS TO THE TRIASSIC PERIODS-DISCOVERY OF NEW ORGANIC TYPES FEATHERED ARCHEOPTERYX OF THE OOLITE.

Theory of Transmutation-Absence of Intermediate Links.

HE most obvious and popular of the objections urged

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against the theory of transmutation may be thus expressed: If the extinct species of plants and animals of the later geological periods were the progenitors of the living species, and gave origin to them by variation and natural selection, where are all the intermediate forms, fossil and living, through which the lost types must have passed during their conversion into the living ones? And why do we not find almost everywhere passages between the nearest allied

CHAP. XXII.

OBJECTIONS TO TRANSMUTATION.

425

species and genera, instead of such strong lines of demarcation, and often wide intervening gaps?

We may consider this objection under two heads:

First, To what extent are the gradational links really wanting in the living creation or in the fossil world, and how far may we expect to discover such as are missing by future research?

Secondly, Are the gaps more numerous than we ought to anticipate, allowing for the original defective state of the geological records, their subsequent dilapidation, and our slight acquaintance with such parts of them as are extant, and allowing also for the rate of extinction of races and species now going on, and which has been going on since the commencement of the tertiary period?

First, As to the alleged absence of intermediate varieties connecting one species with another, every zoologist and botanist who has engaged in the task of classification has been occasionally thrown into this dilemma,-if I make more than one species in this group, I must, to be consistent, make a great many. Even in a limited region like the British Isles, this embarrassment is continually felt.

Scarcely any two botanists, for example, can agree as to the number of roses, still less as to how many species of bramble we possess. Of the latter genus, Rubus, there is one set of forms, respecting which it is still a question whether it ought to be regarded as constituting three species or thirty-seven. Mr. Bentham adopts the first alternative, and Mr. Babington the second, in their well-known treatises on British plants.

We learn from Dr. Hooker that at the antipodes, both in New Zealand and Australia, this same genus Rubus is represented by several species rich in individuals and remarkable for their variability. When we consider how, as we extend our knowledge of the same plant over a wider area, new

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