ISOLATION 191 



from one another. As she works in the hayfields she never 

 confuses orchises with buttercups (Ranunculus), thus showing 

 an interesting and valuable power of discrimination. Never- 

 theless, she is all the while recklessly intercrossing varieties, 

 and species so that if in past times her activity had worked 

 unchecked, it would never have produced any rich diversity of 

 colour in the plant world, but would have left a lack-lustre 

 herd of petty blossoms which would have done nothing to 

 relieve the dull monotony of the green luxuriance about them. 

 But plants are not of a dull monotonous green and there must, 

 therefore, have been some other principle at work, putting a 

 barrier between variety and variety, species and species as 

 new forms arose. This it is, and not her qualified constancy, 

 which has effected the isolation which is the necessary condition, 

 if noble flowers are to result from her work. For insects, un- 

 restricted, would have been authors of confusion and chaos. 



A few examples of the working of insects will show their 

 defects as makers of species. In a field of buttercups there are 

 often two species in blossom side by side, Ranunculus bulbosus and 

 R. acris. The former begins to blossom a good deal earlier 

 than the latter, but the flowering times of the two overlap. If 

 you watch a bee among them she will often for a time keep to 

 one species. R. acris stands up a great deal higher, and, owing 

 to this, she will often for a time pass over R. bulbosus. But 

 before long she will often change her level and busy herself 

 with the lower-growing species. In a bed of mixed polyanthus 

 flowers bees may be seen going from one colour to another 

 heedless of theories and of the claims of polytypic evolution. 

 The same thing takes place when they are busy upon rhododen- 

 drons and columbines of slightly, or even widely, different tints. 

 These instances of infidelity to colour and species I select 

 because I have recently observed them. They are only what 

 might be expected when it is borne in mind that the constancy 

 of the bee is due to her instinctive eagerness to load up with 

 honey with all possible speed, return and unload, then load up 

 again without waste of a moment. She understands her own 

 business, but she cannot be regarded as a good isolator. On the 



