NA TURE 



[March 4, 1909 



interest, and the third is difficult to follow in parts 

 except by readers having some acquaintance with 

 the subject. Probably the work will be best read 

 and appreciated by readers who have already acquired 

 a rudimentary knowledge of scientific principles 

 and desire to know something of the problems and 

 positions of branches of natural Icnowledge beyond 

 the boundary of their own experience. 



A sectional model of the frog, showing the 

 external and internal parts of the animal,, and its 

 development from the fertilised ft^,^ to the stage in 

 which the tail of the tadpole has nearly disappeared 

 and the hind- and fore-legs are present, is presented 

 with the second volume. The model should be of 

 assistance in suggesting instructive observations to 

 the student or teacher of natural historv. 



When the work is completed it will form a verv 

 useful compendium of pure and applied science, and 

 should find a place on the shelves of manv libraries. 

 The editor is to be congratulated upon the plan, and 

 the publishers upon the attractive form in which they 

 have executed it. 



THE EXPERIMENTAL METHOD IN 

 ZOOLOGICAL RESEARCH. 

 Experimental Zoology. Part i., Embryogeny : an 

 Account of the Laws governing the Development 

 of the Animal Egg as ascertained through Experi- 

 ment. By Dr. Hans Przibram. Pp. viii-l-124; 16 

 plates. (Cambridge : University Press, 1908.) Price 

 7s.. 6d. net. 



'T'HE publication of a new work on experimental 

 •L' zoology is a sign of the times. Until com- 

 paratively lately the experimental method was not 

 widely adopted in the pursuit of zoological inquiry; 

 The morphologist, as a general rule, confined 

 his attention to the form and structure of animals 

 and the changes through which these pass in the 

 progress of individu.-d development, without regard 

 to 'the different ways in which form and structure 

 arise in embryogeny and the forces which control the 

 modes of growth. 



The founding of the Archiv fin Enhmckehings- 

 mechanik was a new departure in serial zoological 

 iit'eraturc, and served to emphasise the growing 

 importance of that branch of study which is called 

 developmental mechanics, while the subsequent issue 

 in America of a new journal, The Journal of Experi- 

 mental Zoology; in which the range of subjects dis- 

 cussed is somewhat more extensive, was a further 

 advance in the recognition of the experimental 

 method as a means of- zoological research. Still more 

 recently Prof.T. H. Morgan has published a volume 

 on " Experimental Zoology " in which he deals not 

 only with problems of animal morphologv, but with 

 others which are in their essential nature physio- 

 logical. But physiology, as ordinarily understood, 

 still tends to signify human physiology, and the study 

 of function in the lower forms of life, e\ce]3ting in 

 so far as it serves directly to elucidate the vital pro- 

 cesses of the higher animals, and more particularly 

 NO. 2053, \oi,. 80] 



man, remains as yet a much neglected department of 

 biology. 



Experimental zoology mav be held 10 comprise all 

 those branches of zoological inquiry, whether morpho- 

 logical or physiological, which are conducted by 

 observation combined with experiment. That the 

 fundamental problems in biologv cannot be solved 

 without recourse to the experimental method is a 

 generalisation which zoologists have been a little slow 

 to accept, and the complete absence in this country 

 (and, indeed, in nearly every country) of experiment 

 stations where animals can be kept under constant 

 observation in a natural and healthv environment is a 

 circumstance which contrasts strangely with the com- 

 parative wealth of equipment in other branches of 

 observational science. It is greatly to be hoped, 

 therefore, that the appearance of such works as Dr. 

 Hans Przibram 's, which is to treat of all departments 

 of experimental zoology, will be the means oL com- 

 pelling greater attention to the pressing needs of this 

 branch of study. 



We are told in the preface that the work is to be 

 issued in five parts, each of which is to be complete 

 in itself. The present volume deals with fertilisation 

 and the first development of the individual organism 

 without regard to its origin ; the phenomena of re- 

 generation are to be discussed in part ii. ; variation 

 and heredity in part iii. ; the growth of the developed 

 organism and the relation between the cell nucleus and 

 the cvtoplasm in part iv. ; while the last volume is to 

 be devoted to general physiological problems, including 

 that of sex. The part now under notice is an English 

 translation by Miss Hertha Sollas of a German edition 

 published last year. 



\\"e arc informed at the end of the preface that 

 " the author has read the proofs [of the transla- 

 tion] and has made such additions as were neces- 

 sary to bring it up to date." Nevertheless, we can- 

 not refrain from remarking on the absence of 

 any reference to several not unimportant papers 

 that have appeared in recent years, and in our opinioii 

 the first chapter is calculated to convey a wrong 

 inipression of the present state of the fertilisation 

 problem. Thus it is recorded that Winkler succeeded 

 in fertilising sea-urchin ova with the extracted juice 

 of spermatozoa, but there is no mention of the subse- 

 quent work of Gies (published so long ago as 1901), 

 which showed that M'inkler's results were due to 

 osmotic influences, and not to the action of the sperm 

 extract. Gies's interpretation has since been accepted 

 by Loeb, while Pichou's results (published in 1905) 

 were confirmatory of those of Gies. There is at 

 present no experimental evidence that spermatozoa 

 contain specific substances which, when extracted, are 

 capable of fertilising ova. Again, in the italicised 

 conclusion at the end of the first chapter we read 

 that 



" the cause which determines the transition of the 

 resting animal egg cell to a state of progressive 

 development must be sought in an acceleration of the 

 vital processes which, even in the resting egg, are 

 always going on." 



Loeb, however, has pointed out (1906) that if such 

 a conclusion were correct, normal sea-urchin eggs 



