NOTES AND LITERATURE. 



GENERAL BIOLOGY. 



Vernon's Variation. 1 — Mr. H. M. Vernon off >xford. England, has 



tions on variation made since the publication of Darwin's great work 

 on The Variation of Animals and Plants under Domestication. The 

 book will form a valuable student's manual in the field of general 

 biology. It is clear and concise in style and is remarkably free from 

 technical terms and mathematical formulae, considering the fact that 

 it deals largely with statistical methods. 



It is divided into three parts which treat respectively of "The 

 Facts of Variation," "The Causes of Variation" and "Variation in 

 its Relation to Evolution." 



Part I includes a brief explanation of the statistical methods 

 employed in the study of variation, a remarkably clear presentation 

 of the difficult subject of correlated variations, and a discussion of 

 dimorphism and discontinuous variation, in which the ideas of Bate- 

 son and de Vries receive special attention. 



Part II treats of the effects on organisms of external conditions, 

 such as temperature, light and moisture, a subject discussed more 

 exhaustively by Davenport in his Experimental .\ro>plw!ogy and by 



blastogenic variations contain, along with much other material, an 

 account of important experiments made by the author in the hybridi- 

 zation of various species of echinoderms. Accepting as probably 

 correct the idea of Weismann that variations which are hereditary- are 

 of germinal origin, Vernon believes that the heritage borne by the 

 germ-cell is not at all periods of its existence the same, but that it 

 changes as the germ-cell changes in maturity. Thus when two 

 species of echinoderm are crossed, which ordinarily breed at different 

 seasons of the year, that species impresses its characters most 

 strongly on the offspring which is (at the time the cross is made) 



figs. New York. Henry Holt and Co.. 1903. 



