482 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



" indefinite " variations never occur. Darwin has given plenty of illus- 

 trations of definite, but none of " indefinite results of the changed con- 

 ditions of life." * He says the former are " plentiful." t 



The first essay is " A Naturalist's Contribution to the Discussion of 

 the Age of the Earth." It is a most interesting one in itself ; but we 

 are no nearer the answer to the question — How long does it take to 

 make a species ? Natural selection must, on the laws of chances, require 

 an immense time ; but the law of " response with adaptation " will make 

 one in a few generations, as in pigeons and many cultivated plants ; for 

 differences arise quite equal to those by which some systematists differ- 

 entiate species. The incapability of interbreeding is no test of a species 

 (as Huxley seemed to maintain), as many breed freely together, e.g. Medi- 

 cago sativa x M . falcata, widely grown on the Continent. I have prac- 

 tically turned Ononis spinosa into 0. repens, by growing it in damp soil 

 and air, in two years. % Consequently we need only follow Huxley's 

 advice : " If the geological clock is wrong, all the naturalist will have 

 to do is to modify his notions of the rapidity of change accordingly." § 



Professor Poulton alludes to the many wingless insects in Madeira. 

 Darwin's theory was " that the wingless condition of so many Madeira 

 beetles is mainly due to the action of natural selection, but combined, 

 probably, with disuse." || He refers to the idea that they were blown out 

 to sea ; but as Madeira is thirty-four by twelve miles and Jersey, which 

 abounds in butterflies — much more likely to be blown away than beetles — 

 twelve by seven, it is difficult to accept such a cause of their disappearance. 



The second essay is on the question, " What is a Species? " Evolu- 

 tion, of course, displaced the old idea of fixity of a species, because of its 

 assumed creation once for all ; but from what has been said of all want 

 of basis of the theory of natural selection, one can hardly accept the 

 description of it as a " great motive power to evolution." % According 

 to Darwin it is no " power " at all, but only a metaphor.** 



In discussing cross and self-fertilization of plants, it appears that 

 Professor Poulton is not aware of all that has been written upon the 

 subject.tt It has long been shown that crossing as done by cultivators 

 is only a temporary stimulus, as, indeed, Darwin's own experiments 

 proved, and that the " finer " the "form " of the florist's flower may be, 

 the less chance is there for securing seed ; so that in some cases the 

 "best " die out altogether, just as pigeon-fanciers lament that " the best 

 die in the nest." 



In this essay Professor Poulton touches on direct adaptation, and 

 quotes Professor Farmer as saying that there is " a probable prevalence 

 in the plant- world of a constant specific mechanism that is able to be 

 actuated in different ways by different kinds of stimuli." tt 



This appears to be pretty much the same thing as the power of the 

 protoplasm and nuclei to respond to, and make structures adapted to, the 



* See An. and PI. under Dom. ii. p. 271. 

 t Letter to Professor M. Wagner (Life, &c. iii. p. 159). 

 | Heredity of Acquired Characters in Plants, p. 32, fig. 3. 

 § loc. cit. p. 5. || Oriqin, dc. 1st Ed. p. 136. 



«j[ Essays, p. 58. ** Origin, dc. 6th Ed. p. 63. 



ft See SelJ '-Fertilization of Plants. Trans. Lin. Soc. 1877. 

 Essays, p. 74, note 2. 



