208 



EVOLUTION AND ANIMAL LIFE 



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FIG. 119. Specimens of the stickleback, Gasierostus cataphractus, 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. 



