196 SECRETS OF ANIMAL LIFE 



hibited by types which have, so far as we can judge, 

 very little of the roving spirit in their composition. 

 We are far from saying that there are not tempera- 

 mental rovers among animals. The common crab 

 has been known to journey along the sea-floor 

 for about a hundred miles, and a cod may take a 

 jaunt of several hundreds, but our point is that 

 wanderings like those of locusts and lemmings, 

 badly called migrations, are reactions to lack of 

 food. We have admitted the probability that there 

 might not be these effective racial reactions to-day, 

 had there not arisen long ago variants with a rest- 

 less, experimental, exploring, roving disposition, 

 who conquered difficulties by circumventing and 

 evading them, who went on a journey, discovering 

 the truth of solvitur ambulando; but what we main- 

 tain is that locusts and lemmings are not " rovers " 

 now. In the same way we cannot accept the 

 American biologist's suggestion that " nomadism 

 in man is of the same order as that of birds," for 

 bird-migration is a long-established, smoothly- 

 working, regularized alternation between the feed- 

 ing and resting of the winter quarters and the 

 breeding and nesting of the summer quarters. It 

 probably began in individual variations or muta- 

 tions in the direction of " roving," but the instinct 

 has been established and perfected in definite rela- 

 tion to the actual necessities of nutrition and repro- 

 duction as affected by seasonal changes. 



It is important not to think of the human " rover " 

 as necessarily pathological, for whether he is one in 



