908 



SCIENCE 



[N. S. Vol. XXXIX. No. 1015 



If the section south of Mt. Diablo is con- 

 sidered as a standard for the lone of Cali- 

 fornia it would be interesting to see whether 

 the divisions admitted by Dickerson may be 

 recognized elsewhere. The series is at many 

 points, especially in southern Oregon, ex- 

 tremely thick, and might easily include more 

 than one faunal horizon as yet unrecognized. 



On the whole the writers are in hearty ac- 

 cord with Mr. Dickerson's results. A most 

 valuable point brought out is the discussion 

 of the depths of the water in which the vari- 

 ous beds were deposited. It should be the 

 incentive to further studies of this sort which 

 have been altogether too much neglected. 



Ealph Arnold, 

 Harold Hannibal 



SCIENTIFIC BOOKS 



Artificial Parthenogenesis and Fertilization. 

 By Jacques Loeb. The University of Chi- 

 cago Press, Chicago, 111. 1913. Pp. viii + 

 306. 39 tables and 86 figures. Price $2.50 

 net; $2.68 post-paid. 



As stated in the preface, " Artificial Parthe- 

 nogenesis and Fertilization " is in reality the 

 English translation of an earlier work, " Die 

 Chemische Entwicklungserregung ■ des Tier- 

 isches Eies," enlarged and brought up to date 

 by incorporation of the recent research in 

 the field of development. The realm of arti- 

 ficial parthenogenesis is not a narrow one, by 

 any means. It involves problems of wide 

 physiological interest, the action of ions on 

 tissues, the natural death of cells, immunity, 

 hybridization and organic oxidation, a process 

 coextensive with life itself. Thus we have 

 chapters devoted not only to the history and 

 methods of artificial parthenogenesis, but on 

 " The Eelative Physiological Efficiency of 

 Various Isosmotic Solutions " ; " Chemical 

 Constitution and Eelative Physiological Effi- 

 ciency of Acids " ; " Condition for Matura- 

 tion of the Egg " ; " Heterogeneous Hybridi- 

 zation " ; " Hydrolytic Processes in the Germi- 

 nation of Oil-containing Seeds," etc. The 

 chapters contain a mass of detailed results, 



chiefly those of the author, obtained by 

 almost continuous experimentation over a 

 period of fifteen years. Each is a model of 

 what the experimental method should be — th© 

 observation of certain facts, the formation of 

 provisional hypotheses to explain these obser- 

 vations and, most important of all, the sub- 

 sequent testing of the hypothesis by experi- 

 ment. Only in this way can a mass of 

 unrelated details be welded together into a 

 logical whole presentable to the general reader, 

 as well as the special student of the field of 

 development. 



The more recent discoveries are naturally 

 of greatest interest. One is impressed in 

 reading Loeb's book, with the great variations 

 in the conditions for development among 

 closely related forms — variation in factors 

 which we should expect to be fundamental 

 and universal. Thus we find that the eggs of 

 Strongylocentrotus purpuratus do not develop 

 in neutral sea water, but only in slightly alka- 

 line sea water, whereas the eggs of Arhacia 

 punctulata develop not only in neutral, but 

 even in a slightly acid medium. The response 

 of eggs to different methods of artificial 

 parthenogenesis varies greatly. All grada- 

 tions occur from species which are normally 

 parthenogenetic or occasionally partheno- 

 genetic through those ready to respond to any 

 method, even mechanical agitation, to forms 

 developing only after very special treatment or 

 not responding to stimulation of any kind. 



A similar variation exists in regard to the 

 oxidative process, which is of particular 

 interest for the theory of development. 

 The rate of oxidation in sea-urchin eggs- 

 increases sixfold after sperm fertilization or 

 artificial fertilization. Apparently the sea- 

 urchin egg has come to a rest because some- 

 thing inhibits its oxidations and the sperm 

 can set them going again, with consequent 

 development. With this hypothesis in mind 

 we turn to the starfish egg, only to find that 

 here the oxidations do not increase after the 

 sperm has entered. The starfish egg under- 

 goes a certain amount of development, matu- 

 ration, in sea water and then comes to rest. 

 The entrance of sperm or treatment of some 



