4 AN INTRODUCTION TO SCIENCE 



seaweeds. From many similar observations giving the same 

 result, we formulate the ' ' law' ' that fish which feed in the 

 neighbourhood of rocks are coloured like the rocks and 

 the growth by which the rocks are covered. Asking the 

 question ' ' Why ? ' ' we are led to make an observation upon 

 our own powers of sight, from which we discover that the 

 resemblance in colour causes the fish to be less easily visible. 

 Further, we observe that many other animals are coloured 

 like their surroundings, and from these colligated observations 

 we draw the conclusion that animals are coloured like their 

 surroundings in order that they may escape notice. Again 

 the question ' ' Why ? " is asked. Whose notice do the fishes 

 need to escape? We can think of only two alternatives. 

 It may be an advantage to the fish not to be seen by its prey, 

 or it may be an advantage to it to be invisible to its enemies. 

 Additional observations with regard to protective colouring 

 have to be made. It is found that a tiger marked by trans- 

 verse bars is less easily seen against a background of tall 

 grass and bamboos than an animal uniformly coloured 

 would be, or that the spots on a leopard make it less visible 

 beneath the trees through which the sun is shining. These 

 animals are practically superior to all enemies. They do not 

 need to be rendered invisible to save them from their pur- 

 suers, but to hide them from the creatures they pursue. Is 

 the same true of the fish ? On the contrary, it is found that 

 rock-feeding fish are preyed upon by many larger and more 

 active kinds ; and, further, a study of their food shows that 

 the small shellfish and worms which compose it could not 

 escape, were their tyrants never so conspicuous, and conse- 

 quently the theory is propounded that the fish which feed 

 near rocks are coloured like their surroundings in order that 

 they may escape the notice of their enemies. 



In all scientific investigations the same method is followed 

 observation, colligation, induction and as soon as the 

 stage of hypothesis is reached the process begins over again. 

 Fresh observations are made with a view to determining 



