EDWARD FORBES. 213 



bottom, rather than the depth of the water, that is the 

 predominant factor in determining the nature and the 

 plentifulness of the forms of animals with which the floor 

 of ' the deep sea ' is peopled. 



In addition to the investigations which he carried out 

 into the present distribution of animals and plants, and 

 particularly the laws which govern the occurrence of 

 animals at different depths in the sea, Forbes interested 

 himself greatly as to the causes of the presence of 

 particular types of animal or vegetable life in special 

 regions. As regards this subject, he was greatly assisted 

 by his wide knowledge both of the palseontological 

 department of natural history and also of geology proper. 

 Various of his published writings deal more or less 

 extensively with this problem ; but the one most generally 

 known is his famous memoir ' On the Connection between 

 the Distribution of the existing Fauna and Flora of the 

 British Isles, and the geological changes which have 

 affected their area, especially during the epoch of the 

 Northern Drift J ( ' Memoirs of the Geological Survey of 

 Great Britain,' vol. i., 1846). This memoir affords such 

 an admirable example of the way in which Forbes com- 

 bined and brought into a focus his varied knowledge of 

 zoology, palaeontology, and geology, that it may be well 

 to glance for a moment at some of the results at which he 

 arrived. In so doing, however, it will be best to leave 

 the animals altogether out of sight, and to restrict our 

 attention entirely to the conclusions which Forbes reached 

 as to the origin of the existing British plants, the problem 

 as regards these being of a less complex character than it 

 is in the case of the former. 



