FOOD AND EVOLUTION 77 



essences of seeds and fruits are the most suitable 

 nutriment, and to obtain these the beak is strengthened 

 and sharpened. The necessary crushing is done by 

 the action of the gizzard, which is usually aided by 

 stones or gravel. The hard, conical beak of the finches 

 serves to crack the seeds and fruits of the garden 

 and hedgerow ; the still more massive jaws of the 

 parrots break the hard-shelled fruits of the tropics ; 

 the twisted beak of the crossbill extracts the seeds of 

 pine-cones. In the delicate humming-birds of South 

 America the bill is elongated and the tongue con- 

 verted into a double tube like that of insects. It is 

 used for tapping insects and the nectaries of flowers, 

 which thus give meat and drink to the most exquisite 

 and airy of known beings. 



This brief ' summary ' of vegetarian dietary sug- 

 gests the relation of food to evolution. Plants them- 

 selves have a long history, in which algas and fungi 

 occupy the earlier pages, lichens, liverworts, and 

 ferns the mediaeval sections, whilst gymnosperms and 

 flowering plants bring us to modern times ; and we can 

 follow the adoption of simple plants as food by the 

 more primitive land animals, and the assimilation of 

 the higher plants by animals which had become more 

 specialised. That many-limbed animals live amongst 

 moulds and the few-limbed creatures feed delicately 

 on fruit or nectar is no casual association, but a fact 

 that testifies to the antiquity of the one and the novelty 

 and high place of the other. We shall also find that 

 as many plants chequer the monotony of their diet 



