Orthoplasy with Correlated Variation 203 



o£ the sole becoming of a light colour which approximates 

 the lio-ht colour of the water ivhcn seen from beneath, and 

 the upper side a dull gray or mud colour, approximatmg the 

 surroundings xvlun seen from above} It is probable, there- 

 fore that all these striking adaptations serve the great and 

 prime utility of concealment. If we now revert to the 

 accommodation of the position of the eyes, we find what 

 may be a striking illustration of the operation of organic 

 selection in screening correlated characters. 



For we may assume that so long as the adaptations in 

 coloration, and especially in the position of the eyes were 

 not secured, or were only partially evolved, it would not 

 be of utility for the sole to lie on the side, for the upper 

 side would be exposed to view, and there would be the 

 disability arising from rendering one eye useless, if the 

 fish took such a position. But the coloration, m its 

 turn, could not be acquired through natural selection so 

 long as the insh did not lie on the side. Accordmg y it 

 seems a fair inference that tltis whole group of aelaptattons 

 required sueh a gradual adjustment of the o'«.- that the 

 maintenance of the function of vision unimpaired was 

 absolutely necessary to the sole if he was to escape elimina- 

 tion while gradually, as the adjustments of the position of 

 he eyes went on, he acquired variations placing him more 

 and ire on one side, and also variations in the direction 

 of the requisite protective colouring. The straining of the 



. Professor Osbo.n, who ha, UincBy looUed over the V^'^^^^ ^^\^X;^ 



side of the sole, by throwing Ught upon U with a m.rr ^„,„„.aif. 



.Kecapitulation,' in ^^^'^^^^'^Z^^::^.^.. >n each 

 ferences are ontogen.c, that is that 'h>:y «= ^ ^^^^ 



s::tion™;::r::t;^^^^^^^^ 



