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Show 336 GEOLOGICAL SUCCESSION. CHAP. X. formations, by the physica1 con dI· t·w ns of the ancient areas having remained near1 y .t li e sam e . Let it .b e remem be re d that the forms of hfe, att le· astI tt hose I1n-habiting the sea, have changed almos simu aneous y t h roug l1 ou t the world ' and .t h. erefore under the most 0 ·a tl . different climates and conditions. . onsi er .le pio-l . . VI-cissitudes of climate dunng the pleistocene c Igwus · 1 · d d . d which includes the whole glacia peno ' an npeortieo h'o w little the specific forms of t h e I.n h a b.I t an t s of the sea have been affected. . On the theory of descent, the full mean~ng of the f: ct of fossil remains from closely consecutive format: ons, though ranked as distinct species, being closely related, is obvious. As the accumulation of each formation has often been interrupted, and . as long b~ank intervals have intervened between successive formatwns, we ought not to expect to find, as I attempt_ed to show in the last chapter, in any one or two for~atwns. all the intermediate varieties between the species whiC~ appeared at the commencement and close of these penods ; but we ought to find after intervals, very long as n1easured by years, but only moderately long as measured geologically, closely allied forms, or,. as they have been called by some authors, representative sp:cies ; and these we assured! y do find. We find,. In short such evidence of the slow and scarcely sensible mut:tion o.f specific forms, as we have a just right to expect to find: On the state of JJevelopment of Ancient Forms.-Tbere has been much discussion whether recent forms are more hiahly developed than ancient. I will not here enter o:: this subject, for naturalists have not as yet defined to each other's satisfaction what is meant by high and low forms. But in one particular sense the CHAP. X. STATE OF DEVELOPMENT. 337 more recent forms must, on my theory, be higher than the more ancient ; for each new species is formed by having had some advantage in the struggle for life over other and preceding forms. If under a nearly similar climate, the eocene inhabitants of one quarter of the world were put into competition with the existing inhabitants of the same or some other quarter, the eocene fauna or flora would certainly be beaten and exterminated; as would a secondary fauna by an eocene, and a palreozoic fauna by a secondary fauna. I do not doubt that this process of improvement has affected in a marked and sensible manner the organisation of the more recent and victorious forms of life in comparison with the ancient and beaten forms; but' I can see no way of testing this sort of progress. Crustaceans, for instance, not the highest in their own class, may have beaten the highest molluscs. From the extraordinary manner in which European productions have recently spread over New Zealand, and have ~eized on places which must have been previously occupied, we may believe, if all the animals and plants of Great Britain were set free in New Zealand, that in the course of time a multitude of British forms would be_come thoroughly naturalized there, and would exterminate many of the natives. On the other hand, from what we see now occurring in New Zealand, and from hardly a single inhabitant of the southern hemi .. sphere having become wild in any part of Europe, we may doubt, if all the productions of New Zealand were set free in Great Britain, whether any considerable ~umber would be enabled to seize on places now occupied by our native plants and animals. Under this P~int of view, the productions of Great Britain may be Said to be higher than those of New Zealand. Yet the most skilful naturalist .from an examination of th~ Q |
