Aberrations of Instinct 



peatedly shown, observation in itself is often 

 a snare: we interpret its data according to 

 the exigencies of our theories. To bring 

 out the truth, we must needs resort to ex- 

 periment, which alone is able to some extent 

 to fathom the obscure problem of animal 

 intelligence. It has sometimes been denied 

 that zoology is an experimental science. 

 The accusation would be well-founded if 

 zoology confined itself to describing and 

 classifying; but this is the least important 

 part of its function: it has higher aims than 

 that; and, when it consults the animal upon 

 some problem of life, its method of quest- 

 ioning lies in experiment. In my own 

 modest sphere, I should be depriving my- 

 self of the most potent method of study if 

 I were to neglect experiment. Observation 

 sets the problem; experiment solves it, al- 

 ways presuming that it can be solved; or at 

 least, if powerless to yield the full light of 

 truth, it sheds a certain gleam over the 

 edges of the impenetrable cloud. 



Let us return to the Pelopaeus, to whom 

 it is time to apply the experimental method. 

 A cell has recently been completed. The 

 huntress arrives with her first Spider. She 

 stores it away and at once fastens her egg 

 upon the Spider's belly. She sets out on a 

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