FROM THE EDDYSTONE GROUNDS TO START POINT. 371 



tion of naturalists was directed to the fact that this factor was in all 

 probability of great importance to animals living even at such depths 

 as 30 or 40 fathoms, at any rate in those seas which are subject to large 

 waves and to strong tidal currents. Even since the publication of this 

 suggestive paper the subject does not appear to have received the 

 attention which it deserves. Hunt bases his conclusions not only upon 

 his own observations of objects trawled from a depth of 40 fathoms in 

 the English Channel, but he publishes a letter from Sir George Stokes, 

 in which the subject is treated from a mathematical standpoint, the 

 conclusions being such as to entirely agree with those which had been 

 drawn from observation. Hunt points out in detail some of the 

 adaptations of animals living in shallow water to resist this movement 

 of the waves.* 



(b) Currents. From the point of view of the distribution of bottom- 

 living marine organisms currents are important (1) as the bearers 

 of a large and important food-supply ; (2) as a means of distribution 

 of the larvffi of many animals and the spores of plants ; (3) as 

 induencing in many places the nature of the bottom-deposit ; (4) from 

 the alterations which they may produce in the density and temperature 

 of the water, and (5) from their power of sweeping away such organisms 

 as are insufficiently fixed. 



(c) Tides. It would be beyond the scope of the present paper to 

 enter into a discussion of the peculiar conditions found within the 

 belt of sea-coast which is alternately exposed to the air and covered by 

 the sea with the ebb and flow of the tide. The highly special character 

 of the fauna and flora due to this cause is well known, and has often 

 been described. 



The currents produced in shallow seas, such as those around the 

 English coasts, by the action of the tidal wave, iniiuence the bottom- 

 fauna in the same ways as do currents due to other causes.f These have 

 already been sufficiently indicated, but in the case of the tidal current 

 one important difference must be noted. In the great majority of 

 instances the tidal current runs alternately in opposite directions, 

 and it would not therefore be likely to bring such an abundant food- 

 supply as a steady current progressing at the same rate, nor would it 

 tend to distribute larvte over a very large area. 



This ecj^ual alternation of the tidal current is often greatly modified 

 in the immediate neighbourhood of the coast, especially where bays 

 and inlets of the sea abound. In such localities the current may run 

 for a much longer time in one direction than in the other. 



'o^ 



* For a further discussion of this subject see pp. 375 and 4.^)7. 



t The strength of the bottom tidal current, as indeed of all bottom cm-rents, in the seas 

 around the British Isles is a subject about which definite information is very much needed. 



