536 



NATURE 



[February 23 191 i 



unexplored regions are pointed out, with hints and 

 advice for future students. The folklore of the island 

 is never lost sight of, and many extracts from the 

 Sagas, and much historical matter, are interspersed 

 in smaller print than the bulk of the narrative. 



The writer's love of Iceland is not lessened by his 

 second, and, as he regretfully remarks several times, 

 final visit. It is interesting to note that in his opinion 

 the union between Iceland and Denmark is political 

 only, and that the ties between the two peoples are 

 not likely to become deeper or closer. 



The work is illustrated by many photographs and 

 drawings, and a map of the route followed. Alto- 

 gether it is interesting reading for lovers of Iceland 

 or for prospective travellers over the same ground, 

 although the detailed accounts, evidently intended for 

 future tourists, of the reception, food, lodging, and 

 cost at each stopping place are wearisome. 



We regret that Herr Herrmann, with one excep- 

 tion, always alludes to our countrymen with some 

 contemptuous phrase; the four years' interval has not 

 softened his attitude towards the British traveller. 



M. G. B. 



HEREDITY AND ITS PHYSICAL BASIS. 

 Hereditary Characters and their Modes of Trans- 

 mission. By C. E. Walker. Pp. xii + 239. (Lon- 

 don : Edward Arnold, 1910.) Price 8s. 6d. net. 

 I'^HIS volume deals very clearly and briefly with 

 the whole field of heredity, but perhaps its most 

 interesting feature is the development of a theory as 

 to the relative share borne by the chromosomes and 

 other parts of the sexual cells in the transmission of 

 hereditary characters. Stated somewhat crudely, the 

 theory and the arguments which support it are as 

 follows : — In the chromosomes are represented new 

 characters {i.e. individual variations, mutations, and 

 the like), while other parts of the cell are concerned 

 with the propagation of old-established racial char- 

 acters. That the chromosomes do not bear entities 

 representing all the inherited characters is shown, 

 firstly, by experimental evidence, such as the fertilisa- 

 tion of enucleated Echinoderm ova. For instance, 

 Godlewski fertilised enucleated eggs of sea-urchins 

 with the sperm of crinoids and obtained gastrulae 

 which possessed pure maternal characters only. 

 Second, through the reducing divisions half the 

 chromatin is eliminated frona the mature gametes. 

 In spite of this, all the racial characters are shown 

 by the individual which develops from the fertilised 

 ovum. If one half the entities representing the racial 

 characters of the father are absent from the sperm, it 

 is so improbable as to be almost inconceivable that 

 exactly those characters which are unrepresented will 

 be supplied by the mother, seeing that the entities 

 present in the ovum have been halved in number in a 

 corresponding way. 



Further, the racial characters are blended in in- 

 heritance, while individual variations and new char- 

 acters are transmitted in a Mendelian way, the 

 mechanism for which is supplied by the chromo- 

 somes. That the sexual characters also are propa- 

 gated in this manner was suggested, first by Castle, 

 NO. 2156, VOL, 85] 



who supposed that both sexes were heterozygous in 

 this respect; that is to say, that each individual con- 

 tained both maleness and femaleness, the one latent 

 and the other patent. Difficulties in the way of 

 accepting this theory were removed by the suggestion 

 that one sex was homozygous, its sexual character 

 being recessive, while the other was heterozygous, 

 and showed the dominant character. Credit for this 

 emendation is given by the author to Bateson and 

 Correns, but by right of priority it belongs to Geoffrey 

 Smith. The latter, in his Naples monograph on the 

 Rhizocephala (published in 1906), suggests that in the 

 case of crabs the male is heterozygous since it exhibits 

 female characters when castrated by the parasite 

 saccullna, and must therefore have femaleness latent. 

 The female, on the other hand, under similar circum- 

 stances, never shows male characters. He further 

 surmises that in some parthenogenetic forms the 

 heterozvgous sex was the female, since from it both 

 male and female individuals were at times produced. 



The ever-present question as to the inheritance of 

 acquired characters comes up again for discussion, 

 and the author, who largely follows the sane reasoning 

 of Archdall Reld, concludes that they are not inherited. 

 Among other arguments in support of this view he 

 includes that from the transmission of the characters 

 of neuter individual in ants. This argument, he says, 

 he has only met with twice before, namely, in 

 the "Origin of Species" and in Poulton's "Essays 

 on Evolution." He will no doubt be interested to 

 know that it figures very largely in the controversy 

 between Weismann and Herbert Spencer, published in 

 the Contemporary Review in 1893 ^^^ 1894. 



One more point must be raised, namely, the use 

 of the word "regression" to signify something the 

 reverse of progression, instead of in the special sense, 

 acquired through biometry, in which it is generally 

 used. The author has followed Archdall Reid in this 

 respect, who, in his •" Principles of Heredity," speaks 

 of variations consisting of the addition of a character 

 as progressive, and those resulting in the loss of a 

 character as regressive. We hope he will also follow 

 him in altering " regression " and " regressive " to 

 "retrogression" and "retrogressive" in future 

 editions. E. H. J. S 



GEOLOGY MADE EASY. 

 Geologic Nouvelle. Thdorie Chimiqiie de la Forma- 

 tion de la Terre et des Roches Terrestres. By H. 

 Lenicque. Pp. xvi + 271. (Paris: A. Hermann e; 

 Fils, 1910.) Price 7 francs. 



THE book before us is the work of an engineer 

 who, having discovered that the received doc- 

 trines of geology rest largely on unproved hypotheses, 

 has been impelled to frame a new geology for himself. 

 The French scientific journals having ungratefully 

 met this by a conspiracy of silence, it is left for us ti 

 introduce it to the public. 



This new light in the dark places of the earth 



comes, it would seem from the acetylene lamp; for 



in the principle of that useful invention the author 



finds the clue to many phenomena which geologists 



„ have explained in ways less sensational. Silicates and 



