326 Scientific Intelligence. 



it a rv processes, that the scientific breeder of to-day has come to 

 look upon a given plant or animal as the result of a definite com- 

 bination of heritable physiological factors. The visible charac- 

 teristics of the body give little clue as to what these heritable 

 factors may be. How these factors are determined, and how the 

 offspring from two parents may appear perfectly similar and yet 

 contain vastly different heritable factors, are clearly explained in 

 this interesting little book. 



The bearing of the Mendelian doctrine on the previously 

 widely accepted theories of heredity, variation, and evolution, is 

 fully discussed. The prevalent view that characters acquired by 

 the body from its very beginning as a fertilized egg are in no 

 case capable of transmission to offspring, is well supported by the 

 very recent discoveries. The organism transmits only those 

 characters which it has received from the germ cells from which 

 it has originated, and each germ cell is capable of bearing only 

 one of two contrasted characters, such as difference in color, 

 stature, or other physical or physiological property. 



The entire rewriting of the new edition was necessitated by the 

 rapid growth of the new branch of science with which it deals. 

 The usefulness of the earlier editions should assure a wide appre- 

 ciation of the present volume. "w. k. c. 



2. Plant-Animals : A study in Symbiosis / by Frederick 

 Keeble. Pp. 163, illustrated. Cambridge, 1910 (University 

 Press). — This little volume, one of the Cambridge Manuals of 

 Science and Literature, consists of a most interesting account, in 

 popular language, of the natural history of the minute Turbel- 

 larian worms, belonging to the genus Convoluta. These worms 

 are peculiar in that they can live only when infested with an alga 

 which lives simbiotically within their cells. The structure of 

 both symbionts is described, and the significance of the symbiotic 

 relations explained. w. r. c. 



3. Allgemeine Vererbungslehre / von Valentin Haecker. 

 Pp. x, 392, with 135 figures and 4 colored plates. Braunschweig, 

 1911 (Friedr. Vieweg & Sohn).— This book is based upon the 

 university lectures of one of the foremost German authorities on 

 the subject of heredity. 



After a general discussion of the chemical and physical proper- 

 ties of the cell, and their relation to the phenomena of life, 

 growth, cellular differentiation, sexual differentiation, and repro- 

 duction, the various theories of inheritance are reviewed in their 

 relation to the cytological phenomena. The theories of variation, 

 natural selection, and evolution are taken up historically, and 

 examined critically in the light of the more recent discoveries. 



The Mendelian doctrine is naturally given particular emphasis, 

 and the close agreement is shown between the segregation of 

 characters, the purity of the germ cells, and other Mendelian 

 phenomena, and the visible processes which take place in the 

 cell. 



