BEITISH WARBLERS 



out to see what human creature was in misery. He found 

 that it was a woman rejoicing over a meeting with her long- 

 lost son. Here the respiratory changes and increased secre- 

 tion in the lachrymal glands were the natural expression 

 of joy." Similarity of the organic symptoms at different . 

 emotional periods may therefore be more common in animal 

 life than we imagine, but it remains to be seen wherein exactly 

 its true significance lies. 



We will now compare the motor reactions of the more 

 closely allied forms amongst the warblers, and for such a 

 comparison we could scarcely choose a genus that could afford 

 more suitable examples. The various species in some cases 

 resemble one another so closely that it is only with difficulty 

 that an expert with dried skins before him can detect the very 

 slight differences in shading and form, and if it were not for 

 some specific type of behaviour, recognition in their natural 

 surroundings would be well-nigh impossible. As instances of 

 extreme resemblance we may take the Willow Warbler 

 and Chiff-Chaff, the Eeed and Marsh Warbler, and the Sedge 

 and Aquatic Warbler, and of those which can be readily dis- 

 tinguished, but nevertheless are very much akin, the Blackcap 

 and Garden Warbler, the two Whitethroats, and the Grass- 

 hopper and Savi's Warbler. Since there is such resemblance 

 in their outward appearance we naturally ask ourselves 

 whether it also obtains in their instincts, habits, and emotions. 

 Now we have no palaeontology to guide us as to the course 

 mental evolution has taken, as we have in organic structures ; 

 the past is a sealed book, and I hold therefore that there is 

 much to be learnt from such comparisons. In fact the only 

 method left open to us is to examine and compare the results 

 as they are presented in nature to-day, and decide whether 

 they are such as we should expect to find according to the 

 principles which we lay down. Let us first compare the 

 instincts most familiar to us, namely those connected with 

 reproduction. Both the Willow Warbler and Chirr-Chaff live 

 in a similar environment and possess territories, the boundaries 



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