94 New York State Museum 



tion in more northern areas through the action of cur- 

 rents or floods from the tropics. 



Effects of waves. The waves just about share hon- 

 ors with the tides in making life difficult for shore forms. 

 The influence of wave-shock upon the shore animals is 

 very profound, and the suggestion has been made that it 

 is not too far-fetched to regard the sedentary habit as a 

 result essentially of this factor in the environment. In- 

 deed it is particularly as regards habit and form of shore 

 animals that the influence of waves has been most pro- 

 found. The exact effect of waves upon organisms de- 

 pends upon whether they live on a firm or on an unstable 

 foundation. Animals living on rocks and boulders may 

 have the protection of seaweeds such as our Rockweeds 

 (Fucus) and other brown algae, such as Ascophyllum. 

 The seaweeds form a natural cover and are effective in 

 absorbing the shock of the waves, particularly the long- 

 stranded Ascophyllum. Aside from this the animals liv- 

 ing on rock or other firm foundation meet the condition 

 to which they are exposed by seeking some sheltered posi- 

 tion, by special powers of adhesion, and by a body form 

 which is adapted to lessening friction. Rocks, particu- 

 larly stratified rocks, offer nooks and crevices suitable 

 for hiding and the shore animals also hide under stones 

 as well as the seaweeds. If the rocks are stratified, the 

 amount and direction of the dip of the beds are important. 

 Rocks with a high dip either toward the sea or land, 

 under the effects of erosion, afford many places for 

 shelter and the chances of being dislodged are greatly 

 reduced. When such rocks dip seaward the fauna is on 

 the more sheltered, landward side and is a good fauna. 

 Such sheltered places are often sought for spawning. On 



