COLOURS PRODUCED BY COURTSHIP . 313 



ful and bright, but those were always very shy and 

 difficult to catch ; others were protectively coloured 

 and exactly resembled the sand, rock, or sea- weed, and 

 these when detected were easily captured. Professor 

 W. A. Herdman of Liverpool has also observed the 

 same facts in other groups of marine animals. 



