BY HEBER A. LONGMAN. 37 



But must these questions be arbitrarily put as alter- 

 natives ? To vary the phrasing, was Samuel Butler — 

 ■■ that clever but contradictious writer." as Lankester 

 calls him — justified in opposing " Luck to Cunning ? " 

 Are not both " Luck " and " Cunning" factors in evolu- 

 tionary processes ? 



Theories of variation are incomplete unless they 

 provide for the facts of momentum, or excessive growth, 

 for the tendencies to develop colossal structures such as the 

 huge dorsal plates of the .Stegosaurs, the teeth of the sabre 

 tiger, the antlers of the Irish elk, the tusks of the mammoth, 

 and the horns of the weird Arsinoithcrium. Theories have 

 to be elastic enough to allow for teratological phenomena, 

 for malformations and abnormalities, for such growths 

 as are associated under the term Dysteleology. Some 

 examples, which might be noted here, so far as the individual 

 is concerned, exhibit no principle of radiogenesis, but 

 rather one of orthogenesis almost '" run mad," to our human 

 view, for some of the structures associated with extinct 

 animals appear to have been carried to a degree far in excess 

 of utility. 



Zittel. in the introduction to his well-known text-book 

 of Palaeontology, says : " Evolution in the organic world 

 has not advanced in a simple, straight -forward direction, 

 but in an exceedingly complicated and circuitous." Palaeo- 

 botanists also tell us that the development of plants has 

 sometimes been accompanied by a progress from the com- 

 plex to the simple, which is almost a retrogression.* Such 

 processes are not, of course, the general rule, but they are 

 notable exceptions. D. H. Scott notes that in the evolution 

 of plants there have been long periods of stability — "' that 

 times of comparative constancy have alternated witli 

 intervals of apparently raj^id change." 



In the " Natural History of Plants " (Kerner, trans- 

 lated by Oliver.) which is one of the most authoritative 

 botanical works, the difficulties of theories of progressive 

 development are emphasised. The impossibility is stated 

 of estimating an\- order of plants as being the most highly 



*lScott : " Evolution of Plants," y>. 17. 



