February 25, 1909] 



NA TURE 



48: 



this book in endeavouring to present the position of 

 electrical theory and practice by methods " not in 

 consonance with the conventional forms of mathe- 

 matical symbols." 



There is one matter to which we feel we must 

 refer in conclusion, though it does not affect the 

 general merits of the book. Surely never was an 

 index more curiously compiled since someone wrote, 

 " Mill, on Liberty : do., on the Floss " in a book cata- 

 logue. What can be said of such entries as these? 

 " Both fields interdependent," as a reference to the 

 interdependence of the electric and magnetic fields ; 

 ■" First Consul's opinion"; "Electricity, mystery of, 

 4; physicists cannot explain, 5; contingencies increase, 

 6; reason obvious, 7"; "Whence mechanical 

 work? " If the rest of the inde.x were comprehensive 

 and well-arranged, such peculiarities might be e.xcused 

 as, possibly, intentionally humorous; but unfortun- 

 ately such is not the case. Thus arc lamps are indexed 

 under " Lamps, arc," but incandescent lamps under 

 " Incandescent," and there are no cross-references. 

 Also, in the preface a full list of the names referred 

 to in the book is promised in the index, but the 

 majority are not to be found there. 



Maurice Solo.mon. 



THE CAUSES OF MUTATION. 



Mutatiou et Tramnatismes, Etude sur I'Evolution des 

 Formes vegitales. By L. Blaringhem. Pp. 239; 8 

 plates. (Paris: Feli.xAlcan, 1908.) Price 10 francs. 

 A CCORDING to the mutational view of evolution, 

 •^ *• the kind of variations to the survival of which 

 specific differentiation is due are not such differences 

 between individuals as are always afforded, in any 

 large collection, by fluctuating variability; but varia- 

 tions of an entirely different nature, which de 

 Vries has called mutations. These mutations are not, 

 as repeatedly stated, larger differences than those 

 which are due to fluctuating variability. On the con- 

 trary, the differences between the extreme variants of 

 fluctuating variations are often so large that they 

 cannot escape the notice of the most unobservant ; 

 whereas the difference between the new types (espe- 

 cially when these are elementary species, and not 

 varieties) which arise by mutation are often so subtle 

 that they can often only be detected by an observer 

 with an intimate familiarity with the species in ques- 

 tion. 



The great difference, according to de Vries, between 

 these two types of variation is that the maintenance 

 of any new stage which has been reached by the 

 selection of the extreme variants of fluctuating vari- 

 ability is dependent on the continuation of the selec- 

 tion which produced it, whereas the new types which 

 arise by mutation are independent of selection. Of 

 course, if the new types are sickly or are characterised 

 by the acquisition of new characters which interfere 

 with their attainment of maturity they very soon 

 cease to exist. The point is that the origin of the 

 new type on the latter view is independent of selec- 

 tion, whilst on the former it is due to it; and this 

 holds good for the origin of new types in a state 

 NO. 2052, VOL. 79] 



of domestication as well as in wild nature. The new 

 form " is seen to be very good after, not before its 

 creation." 



But perhaps the most striking difference between 

 the two kinds of variation is that fluctuating vari- 

 ability is exhibited by all animals and plants at all 

 times, whereas mutability appears to be exhibited only 

 very rarely. Indeed, de Vries only found one plant 

 which appeared to be in this state (Oinothera), 

 although he tested a large variety of plants for the 

 purpose. Now, if it is true that evolution is due to 

 the differences presented by mutability, we naturally 

 want to know to what these mutable phases are due ; 

 and it is a paradoxical fact that de Vries should have 

 discovered a great deal about the causes of fluctuating 

 variability and next to nothing about those of muta- 

 bility. A great many of the differences which are 

 classed as fluctuating can be attributed with great cer- 

 taintv to differences of nutrition, and there is a long 

 series of facts (in connection with the limit attainable 

 bv the selection of such variations) which go to support 

 this explanation. 



Of the causes of mutation little is certainly known, 

 though it is generally held that the inception of a 

 mutable phase is caused by some disturbance of that 

 equilibrium in the germ-plasm which expresses itself 

 in the stability of a species which is not in a mutable 

 state. Indeed, the generality of a belief in that form 

 of variation which has since been called mutation, 

 and of this view, as to the cause of it, is witnessed 

 by the existence of a special French word, " affoler," 

 to express the process by which this disturbance of 

 the equilibrium may be effected. The term " affole- 

 ment " is also used by gardeners to signify the state 

 which this brings about, in other words, the mutable 

 phase itself. The book before us is an account of 

 a long series of experiments which M. Blaringhem 

 has conducted on the effect of mutilations on the 

 maize and other plants. He finds that the buds which 

 are produced after such mutilation (such as severing 

 the stem) bear a far larger number of abnormal organs 

 — stems, leaves, flowers, and fruits — than do normal 

 unmolested plants; and, moreover, that amongst the 

 offspring of mutilated plants there occur (i) con- 

 siderable monstrosities; (2) plants which have re- 

 covered the ancestral equilibrium ; and (3) very 

 occasional slight anomalies which constitute varieties 

 and are perfectly new and constant. 



M. Blaringhem has come in touch with the out- 

 skirts of an extremely interesting problem, namely, 

 the effect of the rate, at which vital processes take 

 place, on their normality. It may be that the luxuri- 

 ance of life in the tropics is due to the speed at which 

 ontogenetic processes take place there ; if heat increases 

 the rate at which growth takes place (as it is known 

 to), and increased speed leads to increased variability, 

 the luxuriance o7 tropical life may be simply due to 

 wide range of variations placed at the disposal of 

 natural selection to operate upon. Similarly the 

 enormous speed at which growth proceeds in buds 

 produced on plants which have been cut down to the 

 ground may be the sole cause of the increase in the 

 number of monstrosities produced by them. Here is 

 matter for investigation, the results of which ought 



