NATURE 



[September 13, 1917 



under the restraint of, the other forces inherent 

 in the system. What is known as to the precipita- 

 tion of calcium salts in various colloids, and as to 

 similar phenomena, is used in the interpretation 

 of the spicules of Sponges and Alcyonarians and 

 the skeletons of Radiolarians and Foraminifers. 

 There seems to be much in such formations that 

 is not in any essential way dependent on their 

 occurrence within living- creatures. 



" But every now and then we come to certain 

 deep-seated signs of protoplasmic symmetry or 

 polarisation, which seem to lie beyond the reach 

 of the ordinary physical forces. It by no means 

 follows that the forces in question are not essen- 

 tially physical forces, more obscure and less 

 familiar to us than the rest," comparable, for 

 instance, with the formative force which Lehmann 

 demonstrated in "fluid crystallisation." Crucial 

 experiments are, we admit, awanting, but our faith 

 is strained by the author's physical account of 

 the apparently selective behaviour of certain 

 Foraminifera which make for themselves very 

 effective encasements of particular kinds of 

 materials, such as sponge-spicules. We are in- 

 clined to think, also, that the author exaggerates 

 the fluidity of Alcyonarian "species,", for while 

 his reproach may be justified in some genera, the 

 striking feature in others is the rigid specificity, 

 specimen after specimen like the duplicate of its 

 predecessor, the absence of inter-grades, the clean- 

 cut peculiarity of many of the spicular forms, and 

 the individuality of the architecture around the 

 polypes. 



An attractive chapter deals with the logarith- 

 mic spiral which is of such widespread occurrence 

 among animals, notably among Gasteropods. " In 

 the growth of a shell, we can conceive no simpler 

 law than this, namely, that it shall widen and 

 lengthen in the same unvai-ying proportions : and 

 this simplest of laws is that which Nature tends 

 to follow. The shell, like the creature within it, 

 grows in size, hut does not change its shape; 

 and the existence of this constant relativity of 

 growth, or constant similarity of form, is of the 

 essence, and may be made the basis of a definition, 

 of the logarithmic spiral." From this type have 

 evolved multitudinous diversities of form, mathe- 

 matically identical, and natural selection may well 

 be relieved of the burden of them. Of the author's 

 explanations of horns and phyllotaxis, of the eggs 

 of birds and the tests of sea-urchins, we have no 

 space left to speak. We must, however, direct 

 attention to what seems to us a slight blemish on 

 p. 660, where the author adheres to a mechanical 

 interpretation of the position of the spine on 

 Bilharzia eggs, an interpretation which "destroys 

 the chief evidence for the existence of a supposed 

 new species of worm, a continued belief in which, 

 among worms of such great pathogenic im- 

 portance, might lead to gravely erroneous patho- 

 logical deduction." We do not understand why 

 Prof. Thompson deliberately allowed this to 

 remain, knowing, as a note indicates, of Dr. 

 Leiper's recent work, which does far more than 

 assert that terminal and lateral spined eggs belong 

 NO. 2498, VOL. 100] 



to separate and distinct species of Bilharzia. Is 

 there not a risk that the retention of the page may 

 "lead to gravely erroneous pathological deduc- 

 tions " ? 



With the often fanciful utilitarian interpreta- 

 tions of coloration and markings, of which a 

 deliciously ironical exposition is given, the author 

 contrasts the deep-seated adaptations of structure 

 to mechanical efficiency, seen so well in a bone, 

 where statical and dynamical considerations can 

 be applied and established in detail. The book 

 closes with a luminous essay on "the theory of 

 transformations, or the comparison of related 

 forms," in which it is shown, to put the matter 

 rather roughly, how one harmonious deformation, 

 may lead from one skull or leaf to that of a related 

 I type, how trammels or lines of constraint may 

 j determine the action of the expansive forces of 

 growth, now in one direction and again in 

 another. 



We offer Prof. D'Arcy Thompson felicitations, 

 on his masterly book. It marks a big advance 

 in science, and it will make other advances pos- 

 sible. He has used his own observations and 

 those of a hundred others to show, in a way that 

 will surprise and delight many, what promise there 

 is in the endeavour to carry into the study of 

 living beings the laws and lessons of the inorganic. 

 When first we laid the book down, we were 

 tempted to say, "Magnificent, but not biology,"" 

 but wiser reflections prevailed. Who knows 

 better than the author what biology is and is not? 

 We saw that he was but putting heredity and 

 variation temporarily aside for his purpose, "to 

 show that a certain mathematical aspect of 

 morphology, to which as yet the morphologist 

 gives little heed. Is interwpven with his problems,, 

 complementary to his descriptive task, and help- 

 ful, nay, essential, to his proper study and com- 

 prehension of form." We would go further, and 

 say that his argument, couched in a style that Is 

 always clear and dignified, and at times be- 

 witchingly beautiful, has given us a fresh revela- 

 tion of the unity of Nature. 



J. Arthur Thomson. 



SCIENCE AND INDUSTRY. 

 The Chemistry of Dyestuffs : A Manual for 

 Students of Chemistry and Dyeing. By M. 

 Fort a,nd Dr. L. L. Lloyd. (" Cambridge Tech- 

 nical Series.") Pp. xi + 311. (Cambridge:. 

 At the University Press, 191 7.) Price 75. 6d.. 

 net. 



THIS work, which has the scope of an elemen- 

 tary text-book, Is a useful addition to the 

 rapidly increasing number of manuals in the Eng- 

 lish language devoted to the subject of dyes and- 

 their intermediate products. The authors point 

 out that the opportunity of development now 

 presenting itself to the colour manufacturer in 

 this country will lead to a greater interest In the 

 chemistry of dyes and to an increasing demand 

 for chemists possessing special knowledge of 

 colouring matters. To the student equipped with) 



