No. 643] EFFECTS OF ENVIRONMENT 



151 



a mind, must attend now to a stimulus received from one 

 side, now to that on another. Such vacillation is not con- 

 ducive to the development of higher types of mental life 

 through the delegation of psychic authority to one nerv- 

 ous center. The rocky ocean shores, then, put a pre- 

 mium on radial symmetry and thus as an environment 

 tend to foster psychically unprogressive animals. The 

 barnacles, that appear to have come from progressive, 

 bilaterally symmetrical ancestors, have become degraded 

 with the taking on of the sessile life and radial symmetry 

 that suits them so well to wave-beaten shores. 



The ebb and flow of ocean tides have a pronounced 

 effect on shore animals. Those species that are not able 

 to survive alternating exposure to the desiccating effects 

 of air of varying temperatures and the activity of vio- 

 lently moving water of rather constant temperature can 

 not exist on rooky shores. This fauna must be resii^tnnt, 

 and is so. An anemone can be kept out of water for a 

 week— until it looks like a dried raisin; or kept in a 

 tightly corked l)ottle for ten days, and when replaced in 



two. ISucli nil niiiiiial will iiol rcadil} snccumb to the 

 exposure l)et\veeii tidfs or rviw lo ilir >iai>-iiation likely 

 to occur in a beach pool iliat is cut off from the ocean 

 during a prolon.yvd pci-iod of low watci'. The barnacles 

 and molluscs on rock\ -hoiv- arc i .rotcctr.l liy heavy cal- 

 careous shells. Flatit'ly^ has sivu-uested that land animals 

 perhaps arose in tlie i)ast on ocean beaclies as a result of 

 the resistance develojied dni'ing exposure between tides. 



As a whole tlie environment occurring on rock l)eaches 

 offers abundant food, Imt hard conditions for life. Tlif 

 fauna is highly adapted to resist the two important en- 

 vironmental factors— moving water and exposure to van- 

 nh]o conditions - and in this adaptation the fauna has in- 

 cidi^iitally but of ncccssit)- l)ecome un[)rogressive and cle- 

 \-otos most of its arti\ ities (1) to feeding rapidly when 

 till' o])i)ortunity conies, (2) to resisting, (8) to resting. 



« Scit )!cc rroarcss, 1921. 



