October 30, 1896.] 



SCIENCE. 



627 



moves the whole point from the criticism I 

 have just quoted. According to the Darwin- 

 Wallace theory of natural selection, indi- 

 viduals sufficiently advantageously varied 

 to become the material for a fresh advance 

 when an advance became necessary, and at 

 other times sufficient to maintain the 

 ground previously gained — such individuals 

 existed not only at the opposite ends of the 

 wood, but were common enough in every 

 colony within its confines. The mere fact 

 that an individual had been able to reach 

 the condition of a possible bride or bride- 

 groom would count for much. Few will 

 dispute that such individuals "have already 

 successfully run the gauntlet of by far the 

 greatest dangers which beset the higher 

 animal [and, it may be added, the lower 

 animals also] — the dangers of youth , Nat- 

 ural selection has already pronounced a sat- 

 isfactory verdict upon the vast majority of 

 animals which have reached maturity."* 



But the criticism retains much force when 

 applied to another theory of evolution by 

 the selection of large and conspicuous vari- 

 ations — a theory which certain writers have 

 all along sought to add to or substitute for 

 that of Darwin. Thus Huxley from the 

 very first considered that Darwin had bur- 

 dened himself unnecessarily in rejecting 

 per saltum evolution so unreservedly. f And 

 recently this view has been revived by 

 Bateson's work on variation and by the 

 writings of Francis Galton. I had at first 

 intended to attempt a discussion of this 

 view, together with Lord Salisbury's and 

 other objections which may be urged against 

 it; but the more the two were considered, 

 the more pressing became the claims of the 

 criticism alluded to at first — the argument 

 that the history of our planet does not allow 

 sufficient time for a process which all its 

 advocates admit to be extremely slow in 



*Poulton, Colours of Animals, p. 308. 

 tSee his letter to Darwin, November 23, 1859: 

 Life and Letters, Vol. II. 



its operation. I select this subject because 

 of its transcendent importance in relation 

 to organic evolution, and because I hope 

 to show that the naturalist has something 

 of weight to contribute to the controversy 

 which has been waged intermittently ever 

 since Lord Kelvin's paper ' On Geological 

 Time ' * appeared in 1868. It has been 

 urged by the great worker and teacher 

 who occupied the Presidential Chair of this 

 Association when it last met in this city 

 that biologists have no right to take part in 

 this discussion. In the Anniversary Ad- 

 dress to the Geological Society in 1869 

 Huxley said : " Biology takes her time 

 from geology. * * * If the geological clock 

 is wrong, all the naturalist will have to do 

 is to modify his notions of the rapidity of 

 change accordingly." This contention is 

 obviously true as regards the time which 

 has elapsed since the earliest fossiliferous 

 rocks were laid down. For the duration of 

 the three great periods we must look to the 

 geologist ; but the question as to whether 

 the whole of organic evolution is comprised 

 within these limits, or, if not, what propor- 

 tion of it is so contained, is a question for 

 the naturalist. The naturalist alone can tell 

 the geologist whether his estimate is suffi- 

 cient, or whether it must be multiplied by 

 a small or by some unknown but certainly 

 high figure, in order to account for the evo- 

 lution of the earliest forms of life known in 

 the rocks. This, I submit, is a most im- 

 portant contribution to the discussion. 



Before proceeding further it is right to 

 point out that obviously these arguments 

 will have no weight with those who do not 

 believe that evolution is a reality. But al- 

 though the causes of evolution are greatly 

 debated, it may be assumed that there is 



* Trans. Geol. Soc. Glasgow, Vol. III. See also ' On 

 the Age of the Sun's Heat,' Macmillan, March, 1862: 

 reprinted as Appendix to Thomson and Tait, Nat- 

 ural Philosophy, Vol. I, part 2, second edition, and 

 ' On the Secular Cooling of the Earth, ' Royal Society 

 of Edinlurgh, 1862. 



