NA TURE 



149 



THURSDAY, OCTOBER 23, 1919. 



FACTS AND FACTORS OF EVOLUTION. 

 The Causes and Course of Organic Evolution: A 

 Study in Bioenergics. By Prof. John Muirhead 

 Macfarlane. fp. ix + Sys- (New York: The 

 Macmlllan Co.; London: Macmlllan and Co., 

 Ltd., igi8.) Price 17^. net. 

 "T^HIS book is the outcome of a lifetime of bio- 

 -'■ logical reflection and investigation, and will 

 be read with much interest. The author, who left 

 Edinburgh for Philadelphia many years ago, was 

 early disciplined in zoology, as well as botany, 

 but it is to the latter that he has especially devoted 

 himself as professor in the University of Penn- 

 sylvania. His treatise is erudite and careful, very 

 instructive, even apart from its theories ; it 

 expresses the convictions of a patient and inde- 

 pendent thinker; it states a number of piquant 

 conclusions more or less peculiar to the author; 

 and it is carefully written. It covers a very wide 

 range — the origin of organisms upon the earth, 

 the phylogcny of plants and animals, the evolu- 

 tion of morals and man, the ethical factor in 

 organic evolution, the r61e of religion in the 

 ascent of man, the competitive and the co-opera- 

 tive systems among animals and in mankind, the 

 human environment as it has been and is, and 

 the evolution yet to come. We must restrict our 

 attention to a few of the salient features. 



(i) Prof. Macfarlane notes that "energy, con- 

 tinuity, and evolution," which may be said to con- 

 stitute "the triune basis of existence," form the 

 keynote of his book. But all that is distinctive is 

 the prominence given to "energy." The author 

 recognises a series of forms of energy, which he 

 calls thermic, lumic, tonic, chemic, molic or 

 gravic, electric, biotic, cognitic, and cogitic. 

 Biotic energy is associated with protoplasm in 

 general, cognitic with chromatin, and cogitic with 

 neuratin or Nissl substance. The terms " cog- 

 nitic " and "cogitic" are far from happy, and it 

 is of dubious utility to apply the physical concept 

 of energy to certain aspects of vital activities 

 which remain undescribed when a physical and 

 chemical formulation has been given of the others. 

 If it could be definitely stated — as it cannot — that 

 the particles which ultra-microscopic examination 

 shows in movement in a living nerve-cell are asso- 

 ciated with a particular kind of energy, distinct 

 from and yet in a line with such recognised ener- 

 gies as heat and electricity, then there would be 

 an objective basis for a form of positive vitalism, 

 similar to that held by some modern biologists, 

 such as Prof. Marcus Hartog and the late Prof. 

 Richard Assheton ; but more evidence of the 

 reality of " biotic energy " is required than Prof. 

 Macfarlane adduces — more evidence than the 

 usually admitted inability to give an adequate 

 description of the most characteristic features of 

 the activities of living creatures in physico- 

 chemical terms. The living organism is a riddle 

 imperfectly read, but our confidence in Prof. 

 NO. 2608. VOL. IOa] 



Macfarlane 's contribution is not increased when 

 we find two or three more particular forms o^ 

 energy piled on the top of biotic. 



(2) The author has discovered, he thinks, 

 overlooked factor in organic evolution, which he 

 calls proenvironment — " the resultant response of 

 an organism to the sum-total of all the environal 

 agents that act on it or on any part of it, and 

 which causes the organism to proenviron a course 

 or pathway that is temporarily satisfying to it, 

 and that can alone be taken in virtue of the action 

 of the several environal agents, and the reaction 

 to each of these by appropriate organismal mole- 

 cules." More briefly, Prof. Macfarlane defines the 

 "law of proenvironment" as "the correlated 

 resultant response by any body to the summated 

 correlation of stimulatory action, that leads to a 

 temporarily satisfied state." We rub our eyes; 

 the so-called law of proenvironment takes us back 

 to Herbert Spencer (with his emphasis on equi- 

 librium and "effective response") and farther. 

 Surely it is a commonplace that the lines taken 

 by development and activity alike are result- 

 ants of environmental stimuli acting on living 

 organisation which is internally determined 

 by the inheritance and by previous experi- 

 ences so that its responses are on the 

 whole adaptive. We confess that we see very 

 little in Prof. Macfarlane's discovery, and we 

 doubt whether the capacity of giving a more or 

 less satisfying unified response to a variety of 

 external stimuli is a factor of evolution at all, 

 except in the sense that every organism is a factor 

 in its own evolution. It is a fundamental fact of 

 life. The "five organic factors that are form- 

 producing," the co-operative action of which is 

 "pentamorphogeny," are Heredity, Environment, 

 Proenvironment, Selection, and Reproduction. 

 But there would have been heredity, environment, 

 proenvironment, and reproduction though there 

 were no evolution, and what would Darwin say 

 to leaving Variability out of the Pentarchy? 



(3) The author contends vigorously that "the 

 main and dominant lines of animal evolution have 

 all originated in fresh water or on land, and that 

 only side lines have assumed a marine life, though 

 these have often branched out profusely into 

 species, and even have given off again groups 

 that have in rare cases returned to a fresh-water 

 or a land life." This is a good-going heresy, and 

 the author supports it with learning and ingenuity. 

 It is directly counter to the conclusion of most 

 authorities, who hold that the probabilities are 

 in favour of a marine origin of most of the 

 phyla. Prof. Macfarlane makes out such a strong 

 case that we feel how uncertain these speculative 

 conclusions are. In our ignorance of the actual 

 beginning of most of the phyla it is diflficult to 

 prove the erroneousness of the view that the buds 

 were in fresh water, though the blossoms may 

 have been in salt. We submit, however, a few 

 considerations : 



(a) At this distance of time appeals to 

 present-day numbers of fresh-water and marine 

 species in any particular phylum cannot be 



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