36 , THE ZOOLOGIST. 



student of the dominant phase of thought which now distinctly 

 influences all philosophy, and less evidently moulds ethics and 

 theology as well. Darwinism is no longer the sole property of 

 the naturalist ; it has invaded the " social contract," and the 

 doctrine of " natural selection " as loosely used in social economy 

 is often little different from utilitarianism, or what has been well 

 called the cult of laisser faire. The last remarks are opportune, 

 because Mr. Headley devotes the second part of his book to 

 '* Problems of Human Evolution," and in these pages we can 

 now only refer to his first instalment dealing with the factors of 

 organic evolution. 



Mr. Headley surveys these factors under the usual different 

 classifications, viz. Heredity, Variation and Death, the Lamarck- 

 ian Principle, Natural and Sexual Selection, and Isolation, and 

 describes and estimates their powers from the standpoint of his 

 own analysis. The result is a most readable and instructive 

 representation of much evolutionary evidence with advocacy of 

 " selectionist " principles. (The term " selectionist " must now 

 be recognised ; it is largely used, and seems to have an extra 

 Darwinian definition.) If there were no struggle for existence, 

 manj'^ animals would, in a short time, become dominant by 

 number. We have had many examples given us, and now Mr. 

 Headley, who is an ornithologist, adduces the case of the^House- 

 Martin {Chelidon urhica) : — " It is quite common for them to 

 have three broods in the year, and we are not beyond the mark 

 in allowing them four in each brood. In order to avoid any 

 possible exaggeration, we will assume that each pair has eight 

 young ones each season. At this rate, if there were no deaths, 

 there would in five years be six thousand two hundred and forty- 

 eight House-Martins sprung from one pair." 



We are glad to find our author is free from the crass Carte- 

 sianism so prevalent among many " Neo-Darwinians " of the 

 present day. " The problem of the origin of consciousness puts 

 us on the horns of a dilemma. Either consciousness is present 

 in the lowest forms of life, or else it was introduced at a higher 

 stage of development. The latter alternative is abhorrent to the 

 very principle of evolution. We are driven, then, to believe that 

 even the micro-organisms, whether animal or vegetable, have 

 some consciousness, however dim." 



