224 SCIENCE PROGRESS 



ridicule seems to me quite as worthy of credence as the view 

 that the factor for the fineness of merino wool was present 

 in the protozoan ancestor of the sheep. 



While every one must welcome the brilliant and most 

 important work being done by the Mendelians and cytologists, 

 which has given us so much new light on the nature of heredity, 

 we cannot admit they have helped us much to an understanding 

 of the processes of evolution. They have shown us some 

 reasons why each generation resembles the previous, but they 

 have not thrown the faintest ray of light on the problem of 

 why it is, though there is no manifest difference between two 

 succeeding generations, that if we take the first and last 

 of 10,000 or 100,000 generations, the differences are very 

 appreciable. They even go the length as Prof. Bateson does 

 of denying the fact, though the fact is beyond question. 



Thanks to the brilliant palaeontological work of Leidy, 

 Cope, Marsh, Osborn, and others we have a very fair knowledge 

 of the evolution of the horse, the camel, the rhinoceros, the 

 titanothere, and of a number of other mammalian types. 

 The experimenters discuss whether evolution took place by 

 loss of factors, or by cross breeding, by slow changes or by 

 rapid leaps : the palaeontologist shows how it did take place 

 and demonstrates that the evolution was gradual as held by 

 Darwin, notwithstanding the remarks of Bateson. 



When Marsh first called attention to the three or four most 

 striking stages in the evolution of the horse, one might perhaps 

 fairly have argued that the stages were too few to prove much ; 

 that there was no evidence that a Mesohippus had not more or 

 less suddenly arisen from an Eohippus ; and that there was no 

 clear evidence of any gradual alteration. Now, however, all 

 this is changed, and the difficulty is to define the limits of a 

 genus like Eohippus, or of a species like Mesohippus Bairdi. 

 The genera and species pass almost imperceptibly into others. 

 The small low-crowned molar of the early Hyracotherium has 

 slowly and steadily through perhaps 3,000,000 years evolved 

 into the large complicated grinder of the modern horse. Are 

 we to believe that this was because Hyracotherium had in it the 

 factor for producing a horse-like molar ? 



Cope has shown that the Phenacodus-like molar is the 

 ancestral type from which all ungulate grinders are derived. 

 Must we believe that the small Phenacodus-like form which 



