January 10, 1913] 



SCIENCE 



65 



standard work so soon after the publication of 

 the third (1909) is convincing evidence of its 

 usefulness. Indeed there is no other recent 

 work which deals with such a wealth of ma- 

 terial of general biological significance ; and 

 there are few biologists who possess Professor 

 Hertwig's facility for clear and forcible pre- 

 sentation. The book is thoroughly readable. 

 Each edition has been an improvement over 

 the preceding, and the present is no exception, 

 through elimination in a few places, but 

 mainly by the addition of entire new sections, 

 and by incorporation of later results in many 

 places throughout. Thus the new matter of 

 the present edition includes the action of ^ 

 and y rays on animal and plant tissues, re- 

 sults of tissue culture methods, and the sub- 

 ject of sex-determination. The subjects of 

 chondriosomes, chemotherapy, dimorphism of 

 spermatozoa, heterochromosomes, graft hy- 

 brids, hormones, secondary sexual characters 

 and inheritance of acquired characters have 

 been thoroughly revised and brought up to 

 date. These additions and revisions are those 

 noted in the preface, but the revision runs 

 pretty well through the book. 



A great merit of the book is that the author, 

 though zoologist, by no means limits himself 

 to animals in the discussion of biological 

 principles, but makes free use of botanical re- 

 sults throughout. His botanical illustrations 

 are often very illuminative, and the constant 

 combination of animal and plant material 

 serves to emphasize the conception of general 

 biology as treatment of the phenomena of life 

 common to animals and plants. 



Professor Hertwig still opposes the preva- 

 lent view that the problems of biology are 

 fundamentally problems of physics and chem- 

 istry. Even if we were to assume, he asserts, 

 that at some remote time the science of chem- 

 istry should be so developed as to reveal the 

 structure of all possible albuminous molecules 

 and their derivatives, and that it provided 

 methods by means of which we could ascertain 

 what kinds of albumen and other organic 

 molecules were present in the cell and in what 

 quantities, we should not thereby gain insight 

 into the essence of the living cell and of proto- 



plasm. And why? Because the cell is not 

 " living albumen," as has sometimes been said, 

 or a mixture of innumerable albuminous mole- 

 cules, but an organism composed of determi- 

 nately arranged vital units, which are again 

 complexes of albuminous molecules and there- 

 fore endowed with properties as different from 

 the properties of the simple albumen molecule 

 as the latter from the constituent atoms. 



It is perhaps presumptuous, even in so sea- 

 soned and honored a veteran as Professor 

 Hertwig, to venture to lay down the limita- 

 tions of chemical research with reference to 

 biology, and the bounds of the insight that fu- 

 ture advance may yield into biological prob- 

 lems, for a reason that will appeal only to 

 those biologists who still use " vital units " in 

 thinking and conceive they know their prop- 

 erties. In any event, such a point of view has 

 its obvious limitations, and they are felt in the 

 treatment of many subjects in the book. On 

 the other hand, this exclusively biological atti- 

 tude is often of the greatest value in the 

 criticism of premature or narrow generaliza- 

 tions of bio-chemists; and in several places 

 Professor Hertwig's broad outlook on the bio- 

 logical field more than compensates for under- 

 estimation of the chemical side. 



The treatment of a few subjects still re- 

 mains rather antiquated. For instance, in the 

 chapter entitled " Untersuchungen der einz- 

 elnen Eeizarten " there is not a single citation 

 more recent than 1891. And in this connec- 

 tion it is surely a serious defect in a work on 

 general biology that the field of animal be- 

 havior should be entirely neglected. Another 

 illustration of antiquated treatment occurs in 

 the discussion concerning " Befruchtungs- 

 bediirftigtkeit der Zellen," where the whole 

 discussion, so far as infusoria are concerned, is 

 based on Maupas' work, while the more recent 

 work of Calkins, Woodruff and Jennings, is 

 not even cited. But in most subjects such 

 neglect of recent work is not so obvious, though 

 piety towards pioneers is always observed, as 

 is fitting. 



The theoretical foundation of the whole 

 treatment remains as before ; if it is sometimes 

 unduly prominent, or even, as it seems to the 



