VI.] INTRODUCTION. 



XCIX 



stream does not set upon any part of that coast. All 

 the driftwood that was washed ashore was of Norway 

 fir, and came from the opposite coast. Dr. Lukis in- 

 forms me that the Gulf- stream has now been ascer- 

 tained not to impinge on any part of the Channel Isles, 

 although the Sargasso weed and the seeds of tropical 

 plants are occasionally thrown up on those shores, after 

 having been deflected and drifted by marine currents. 

 Much evidently remains to be done in defining its exact 

 course in northern latitudes, and in making accurate 

 observations as to its influence on the fauna and flora, 

 as well as on the temperature, of different parts of 

 Europe. 



CHAPTEK VI. 



HABITAT. 



STATIONS. ZONES. ABUNDANCE OF MOLLUSCAN LIFE. GEOLOGI- 

 CAL RELATIONS. CHANNEL ISLES. EXOTIC AND SPURIOUS SPE- 

 CIES. SEA-SIDE SKETCH. 



Stations. — The subject of this chapter is closely con- 

 nected with that of the last ; but it seems more conve- 

 nient to divide it. Having considered the British Mol- 

 lusca with reference to their European and general 

 distribution, I now propose to give a short account of 

 their native habitats and to take a home view of the 

 matter. 



The MoUusca may be divided into land, freshwater, and 

 marine. Their respiratory organization mainly results 

 from the nature of their habitat, or, as botanists would 

 term it, their " station.^^ All land-snails breathe the free 



e.2 



