viii PREFACE. 



pollicis longus, or the hippocampus major 

 about whose very existence they are ignorant, 

 and whose names suggest to them nothing 

 but unpleasant ideas. What they want to 

 find out is how the outward and visible forms 

 of plants and animals were produced. The) 

 would much rather learn why birds have 

 feathers than why they have a keeled ster- 

 num ; and they think the origin of bright 

 flowers far more attractive than the origin <>t 

 monocotyledonous seeds or exogenous stems. 

 It is with these surface questions of obvious 

 outward appearance that I have attempted 

 to deal in this little series. My plan is to 

 take a simple and well-known natural object, 

 and give such an explanation as evolutionary 

 principles afford of its most striking external 

 features. A strawberry, a snail-shell, a tad- 

 . a bird, a wayside flower these are the 

 sort of things which I have tried to explain. 

 If I have not gone very deep, I hope at 1 



