208 



EVOLUTION AND ANIMAL LIFE 



-lilt- 4 'f ' f *• •^i'VLr^ vr^i'*-"' '* -^z::^ 





^^ 



'!% ' 



.^ 



-1 



;-^J 



Fig. 119. — Specimens of the stickleback, Gasterostus cataphr actus, collected in different 

 kinds of water, and showing marked variations in the number of lateral bony- 

 plates and in the size of the dorsal fin rays; at the top, specimens collected in the 

 salt water (note many lateral plates and large dorsal fin rays); next figure below, 

 specimens collected in brackish water; next below, specimens collected in a river 

 mouth; at the bottom, specimens collected in a river, with no lateral plates and 

 small dorsal fin rays. 



