A EATIONAL HYPOTHESIS 509 



this of the simplest organism, because it would commit him to 

 the doctrine of spontaneous generation of organisms of every 

 degree of complexity. 



If the barren facts under such a theory may receive a 

 rational explanation under another theory, the naturalist 

 should use this as the means of penetrating the mystery of 

 the origin of species, holding himself ready to lay it down 

 when it shall prove as useless for the further advance of 

 science as the long serviceable theory of special creations, 

 founded on genetic resemblance, now appears to be. 



Only the application of these principles could explain ration- 

 ally the apparent anomalies of the Australian Flora, its ancient 

 types reinforced by European migrants whose course could be 

 traced along the intermediate highlands, and its two southern 

 comers, only recently joined by the rise of the barren land 

 between, possessing each the remains of separate floras de- 

 veloped on different portions of a large but now vanished 

 Antarctic continent. -^ 



The Tasmanian Introduction was for the scientific world \ 

 only. Hooker was right in his estimate of its popularity, though ^ 

 wrong about the ' Origin,' which had an unimaginable success, 

 the first edition being sold out at once on the day of publica- 

 tion, November 24. Thus he writes to Darwin in April (?) 1859 : 



From what Boott said I thought Lyell had exceeded so 

 much my estimate of the public's interest in such works, 

 that I could not help saying so to Boott. How glad I shall 

 be if it proves the contrary for Science's sake. As to my 

 Essay, if Keeve does not print it separately [this was done] 

 only 150 copies will be printed and 75 sold, as of the Flora 

 Tasmanica ; if he does, I shall buy 100 for distribution, and 

 the sale of the remainder will, judging from the New Zealand 

 Essay, be 2 copies ! In point of sale or awakening interest 

 our books cannot interfere — the number who read both will 

 be inconceivably smaller. 



The publication of the i Origin ' ehcited the following : it will 

 be noted how Hooker continued to lay more stress on factors 

 other than Natural Selection. 



