ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 27 



appearance in a zygote of some of the properties of the gametes." " A 

 zygote has this property of one of the preceding gametes, and that pro- 

 perty of another, in virtue of the operation of what we call heredity ; it 

 has a third property, possessed by neither of the precedent gametes, in 

 virtue of the action of variation." But perhaps it is simpler to say that 

 in asexual reproduction the expression of the inherited qualities tends in 

 development to result in a complete genetic resemblance, while in sexual 

 reproduction the expression of the inherited qualities tends in develop- 

 ment to result in a new individuality. It seems to us preferable to 

 retain the word heredity as a term for the relation between successive 

 generations. 



In conclusion, Mr. Sedgwick suggests that the result of continual 

 selection will be to diminish the variability of a species, and if carried 

 far enough, to produce a race with so little variability, and so closely 

 adapted to its surroundings, that the slightest alteration in the conditions 

 of life will cause extinction. But if selection tends to diminish the 

 variability of a species, then it clearly follows that, as selection has been 

 by hypothesis the most important means of modifying organisms [evolv- 

 ing species?], variation must have been much greater in past times than 

 it is now. In fact, it must have been progressively greater the further 

 we go back from the present time. " Following out the same train of 

 thought, we are inevitably driven to the conclusion that one of the most 

 important results of the evolutionary change has been the gradual increase 

 and perfection of heredity [completeness of hereditary resemblance?] 

 as a function of organisms, and a gradual elimination of variability." 



Statistical Study of Variation.* — Prof. C. B. Davenport has pub- 

 lished a very useful little book giving a simple presentation of the 

 newer statistical methods in their application to the study of organic 

 variation, or, as he (mistakenly) calls it, biological variation. Chapter L 

 deals with the methods of measuring organisms ; Chapter II. with the 

 seriation and plotting of data and the frequency polygon ; Chapter III. 

 with the classes of frequency polygons ; Chapter IV. with correlated 

 variability ; Chapter V. with some applications of statistical biological 

 study. Then follow tables of much convenience for actual work. The 

 book is marvellously terse, but we wish that it had been less so ; we 

 hope that its extensive use will ensure a demand for a second edition in 

 a short time, and that the author will then rewrite the introduction and 

 add a sketch — historical and prospective — convincing the unimpressed of 

 the value of this new departure. 



This statistical study of variations is of great importance, not only 

 to evolution doctrine, but to a sound taxonomy (for it is time that tho 

 diagnosis of a species on two or three specimens should be ruled out of 

 court in cases where hundreds are readily procurable). Therefore we 

 would direct attention to two other introductions to the subject, viz. 

 G. Duncker's ' Methode der Variationsstatistik,' f his article 'Varia- 

 tion-statistics in Zoology,' J and Mr. H. M. Kyle's lucid article, ' An 

 extension of the method of treating variations, with examples and certain 



* ' Statistical Methods, with Special Reference to Biological Variation,' New 

 York and London, 1899, vii. and 148 pp. 



t Leipzig, 1899, 8vo, 75 pp. Bibliography of 111 papers. Reprint from Arcli. 

 Entwickruecb., viii. J Natural Seance, xv. (1899), pp. 325-36. 



