158 THE SCOTTISH NATURALIST 



should they return, are given a fair chance to continue the 

 course of life that adds such a charm to that most beautiful 

 of Highland beauty-spots Loch an Eilein. 



THE FAUNA OF A COAL-PIT AT GREAT 



DEPTHS. 



By James Ritchie, M.A., D.Sc, The Royal Scottish Museum. 



To one unacquainted with the extraordinary adaptive powers 

 of most animals, it must seem a strange thing that in the 

 peculiar conditions of a coal-pit a regular fauna should exist. 

 Yet the thirteen different species of animals mentioned 

 below, all discovered at a great distance from the surface, 

 probably represent only a fraction of the denizens of the pit, 

 and the majority of these appear to be well established, 

 living and breeding in the workings in considerable numbers. 

 Obviously the fauna is an introduced one, for a coal-pit is a 

 very recent earth cavern, and could scarcely have become 

 stocked with a fauna evolved through a long period to suit 

 its peculiar conditions. Nevertheless it bears some relation- 

 ship to a true cave fauna, the original members of which 

 also at one period migrated, by chance, force, or preference, 

 from the outer air, and under peculiar conditions either 

 succumbed or adapted themselves to a new environment. 

 The coal-pit fauna typifies early stages in the formation of a 

 cave fauna. It is indeed an incipient cave fauna, in which we 

 see three distinct processes : the introduction of a miscellaneous 

 set of animals; the weeding out of such as are quite unsuited 

 or inadaptablc to the underground life ; and the establish- 

 ment and spread of more adaptable forms. In this lies the 

 chief interest of the inhabitants of the coal-pit that they 

 illustrate the first effects of a peculiarly stringent process of 

 selection. 



