372 



SCIENCE. 



[N. S. Vol. XXII. No. 560. 



tioned. The reviewer is convinced that as 

 good an argument might be made from the 

 zoological side as de Vries has made from the 

 botanical. Undoubtedly many, if not most, 

 of the characteristics of the races of domesti- 

 cated animals and probably of feral species 

 have arisen by mutation. Take, for example, 

 poultry. The qualities that differentiate them 

 are of the order of mutations — feathered feet, 

 rose comb, elongated tail, taillessness, silky 

 feathers, frizzled feathers, cerebral hernia, 

 polydactyl feet, albinism and many others. 

 All the evidence we have goes to show that 

 these have arisen suddenly, and none of 

 them is halved in cross-breeding. Various 

 wild birds show these same qualities and we 

 must conclude that in wild species also these 

 characteristics have arisen suddenly. Thus we 

 have various wild birds with crests like the 

 Polish fowl {i. e., the iimbrella bird, Cephalop- 

 terus) ; there are ' cross bills,' showing an ab- 

 liormality not uncommon among poultry; 

 there is a syndactyl species of monkey; and 

 there are hairless species of mammals. The 

 long tailed condition of certain Japanese 

 fowl is exactly duplicated in the widow-bird 

 (Chera). . There is hardly a sport not actually 

 prejudicial to the well being of animals which 

 is not realized in some species. 



On the other hand, it is certainly true for 

 zoology that many species are based chiefly on 

 ' more ' or ' less ' of a certain character than 

 an allied species. Further, since animals have 

 a more definite form than plants, and one less 

 modified by variations in environment the 

 fact of geographic variation is a striking one. 

 Now in geographic variation the forms of 

 adjacent localities are distinguished by dif- 

 ferences of the order of fluctuating variants ; 

 the mode being different in each place ; yet the 

 differences between remote localities are of the 

 order of mutations. Geographic variation has 

 been repeatedly observed among birds, fishes, 

 insects and moUusca. It is, of course, possible 

 that the absence of discontinuity in the species 

 may be due to hybridization with blending of 

 characteristics, but blending of characteristics 

 is not so common among hybrids as to justify, 

 oft'hand, such an explanation. That there is 



evidence of evolution without mutation can 

 not be denied. 



The distinction between species and varieties 

 is clearly expressed by de Vries, but it is 

 doubtful if it will be of wide service because 

 of the difiiculty of distinguishing between a 

 'new.' character and an 'atavism.' De Vries 

 admits (p. 564) ' It is often difiicult to decide 

 whether a given form belongs to one or an- 

 other of these two groups.' We look with 

 interest to the experimental testing of de 

 Vries's distinction in animals. 



As to the literary qualities of the book, one 

 has first to praise the general method of ex- 

 position. It is quite a model. Apart from 

 an occasional non-idionlatic phrase or inapt 

 word the diction is good; but much ,of this 

 success is of course due to Dr. MacDougal's 

 careful editing. It is unfortunate that the 

 proof reading has been rather carelessly done 

 and that commas are so atrociously misplaced 

 as often to obscure the sense. Otherwise the 

 publishers have done their part well. The 

 broad margins leave plenty of room for the 

 reader's remarks and memoranda which so 

 suggestive a book tends to call forth in great 

 number. 



De Vries's book is one to read and reread 

 and then to act upon. We would not wish it. 

 less clear cut in its presentation, for then it 

 might merely amuse. As it is it gives a 

 stimukis to the experimental testing of his 

 broad generalizations and iconoclastic con- 

 clusions. 0. B. Davenport. 



Theoretical Chemistry from the Standpoint of 

 Avogadra's Rule and Thermodynamics. By 

 Professor Walter ISTernst, Ph.D., of the 

 University of Gottingen. Revised in ac- 

 cordance with the Fourth German edition. 

 Translated into English by Robert A. Leh- 

 peldt. London and New York, Macmillan 

 and Company, Limited. 1904. Pp. '111. 

 The appearance of the fourth edition of 

 this valuable treatise will be welcomed by all 

 advanced workers in the field of physical 

 chemistry. The general character of this work 

 is too well known to call for special comment. 

 It is distinctively an advanced work, and 

 adapted only to those who have already a good 



