162 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



type. It had broad oval leaves, but it lived on rocks within the moisture 

 of a waterfall. 



Dr. Morgan declines to follow Darwin's acceptance of Lamarck's 

 application of disease as the cause of atrophy, as in the case of blind 

 animals living in the dark. " The connection that appears to exist 

 between the degeneration of a special part and the environment in which 

 the animal lives finds its explanation simply in the fact that the environ- 

 ment makes possible the existence of that sort of mutation in it " (p. 356). 

 This would imply that blind animals can only live in the dark. 



Similarly he argues " an animal does not become degenerate because 

 it becomes parasitic, but the environment being given, some forms have 

 found then' way there " (p. 357). Dr. Morgan in thus arguing ignores 

 the enormous amount of inductive evidence based on the accumulation 

 of coincidences between blind animals and darkness, and between parasites 

 (both animal and vegetable) and their hosts — evidence which satisfies 

 the soundest logic. 



Referring to the usual view that " roots in dry soil are diverted to 

 more favourable positions by the presence of greater quantities of 

 moisture," he says: "This may, I venture to suggest, be putting the 

 cart before the horse. The plant may be only able to exist whose 

 responses are suited to certain external conditions, and these determine 

 the limits of distribution of the plant." This will hardly explain the 

 fact that " a poplar sent a root 30 feet horizontally, including its dip 

 beneath the foundations of a wall, and then passed into an old well to 

 the depth of 18 feet."* In the deserts of Damaraland the 'Narras,' a 

 spinescent cucurbitaceous plant, sends its roots downwards 40 feet to 

 reach the water-level. 



In his " Summary " the author admits that " no attempt has been 

 made to account for the causes or the origin of the different kinds of 

 variation " (p. 452). This is to be regretted, because it is by no means 

 so difficult a task, though we can never unravel the mystery of life and 

 its functions ; but admitting a responsive power in protoplasm and the 

 nucleus, everything else follows in securing adaptations. 



Again, he would separate the " origin of species " and " the meaning 

 of adaptation," failing to see that adaptive characters are identical with 

 specific. Thus, species of British euphorbias are known by their vegetative 

 characters as much as by their inflorescence. Similarly, the South African 

 types are known by their massive succulent stems. Both are adaptations 

 to the climates of England and South Africa respectively. On the other 

 hand, Dr. Morgan thinks that " it seems probable that, in general, organ- 

 isms do not respond adaptively to the environment and produce new 

 species in this way ; and, in the second place, there is no evidence to show 

 that variation from internal causes is so regulated that only adaptive 

 structures arise." The latter sentence is true ; a plant responds to 

 environmental conditions, but many structures are not of any benefit 

 to it. Thus drought causes the arrest of branches and leaves, and 

 hardens the woody tissues, so that spinescence is often the result, and 

 a stunting of the plant ensues. Comparing such a plant of the desert 

 with another of the same kind grown with plenty of water, the latter will 

 * Lindley's Theory of Horticulture, p. 1 ( J. 



