20 Descendenz und Hybriden. 



Metcalf, M. M., Determinate iMutation. (Science. N. S. 

 Vol. XXI. p. 355-356. Mar 3. 1905.) 



States that most of the mutants seen by de Vries and 

 also by M a c D u ga 1 have appeared more frequently than would 

 be natural were the mutations vvholly fortituous and indetermi- 

 nate. Considers this of much interest in bearing out the pa- 

 leontological evidence in favor of determinate Variation. 



H. M. Richards (New York). 



Pearl, R., Note on theVariation in the Ray Flowers of 

 Rudebeckla. (Am. Nat. Vol. XXXIX. p. 87—88. 1 fig. 

 Feb. 1905.) 



Count of 430 heads of Rudebeckla liirta, which gave the 

 mean number of ray flowers as 11,365. The most frequent 

 was 13. H. M. Richards (New Yorit). 



Vries, Hugo de, Species and Varieties: their Origin by 

 Mutation. Edited by D. T. Mac Dougal. (XXIII -f 830 pp. 

 Open Court Pub. Co. Chicago. 111. 1905. $ 5.00; 21 shill.) 



It is impossible in the limits of a brief abstract to do justice 

 to the wealth of material found in this volume. A Condensed 

 summary of the table of Contents will, however, give some idea 

 of the topics taken up. The twenty eight chapters are grouped 

 under six heads and these are treated here seriatim. 



Group A, constituting the flrst chapter, which gives a 

 general survey of the field of descent. 



Group B, comprising chapters 2 to 4, treats of elementary 

 species in nature and under cultivation, and their selection. 



Group C, chapters 5 to 10, takes up the matter of retro- 

 grade varieties and some of the questions considered are as 

 follows, characters of retrograde varieties, differences from ele- 

 mentary species, latent characters, correlative variability, Com- 

 pound characters, stability and real atavism, digressive evolution, 

 Crossing of species and varieties, Mendel's law. 



Group D has to do with eversporting varieties and in- 

 cludes chapters 11 to 15. Striped flowers, monstrosities and 

 so forth are described and the questions of the inheritance of 

 monstrosities, of half and middle races is considered. 



Group E, chapters 16 to 34, deals with mutations, and is. 

 naturally the largest of the six groups. The subject is intro- 

 duced by a consideration of the peloric Linaria, from which 

 the author proceeds to the mutations of Oenotliera. These are 

 naturally considered in detail. The facts presented lead to a 

 discussion of the laws of mutability, and analysis of the signi- 

 ficance of these sudden and repeated leaps from an unchanging 

 main stem, of the constancy of the new forms and of the various 

 directions in which the mutations take place. In chapter twenty 

 the question of the origin of wild species is presented and 

 foUowing that the appearance of mutations in horticulture. The 



