European animals : their geological history and geographical distribution / by R.F. Scharff.

  • Scharff, R. F. (Robert Francis), 1858-1934.
Date:
1907
Catalogue details

Licence: In copyright

Credit: European animals : their geological history and geographical distribution / by R.F. Scharff. Source: Wellcome Collection.

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    a powerful barrier formerly existed which separated these two areas. We can thus ascertain the gradual changes which have occurred in the distribution of land and water in Europe. From a careful study of the general range of groups of species, we can gather also the direction of their advance. We have been able to trace, in this manner, that large assemblages of animals issued from various parts of Europe, invading new territories like conquering armies, and sometimes after their retreat leaving a few stray members behind as a standing testimony of their former invasions. Island faunas are particularly useful in aiding us to estimate the comparative ages of such waves of invasion, for they frequently preserve the traces of the latter much longer than the continents, where, owing to keener competition, faunas are subject to more rapid modification. We need not use for our purpose species of animals which might owe their dispersal to such accidental means as I alluded to. For instance, in the nest of the small yellow ant, which lives in this country, as a rule, under stones or clods of earth, we frequently meet with a minute white woodlouse (.Platyarthrus Hoffmanseggii) (Fig. i). It lives in company with the ants and is unmolested by them. The latter apparently do not provide for it in any way, though it is quite blind. Now the same species of woodlouse occurs again in the burrows of the yellow ant in France. Here is a case, then, of a small and incon- spicuous object, which yet could not possibly have passed from the one country to the other except by means of some former continuity of land. I have now endeavoured to give some of the reasons for my belief in the profound importance of the present geographical distribution of animals as an indicator of their geological history. But we possess still other means to aid us in unravelling the history of our European fauna. Though it is evident that, in the vast majority of cases, land and fresh-water animals leave no perceptible trace of their former presence, yet much has been preserved to us, and these