LITERARY NOTICES. 



79 



the species, be assumed as equally or even more 

 operative through long anterior periods, this 

 would account for the diversification of an orig- 

 inal species of a genus into several or many 

 forms as diflereut as those we recognize as spe- 

 cies. But this would not account for the limita- 

 tion of species, which is the usual characteris- 

 tic, and is an essential part of the idea of spe- 

 cies. Just this is accounted for by natural selec- 

 tion. This now familiar term, proposed by Dar- 

 win, was suggested by the operations of breed- 

 ers in the development and fixation of races 

 for man's use or fancy— breeding in each gen- 

 eration those individuals only in which the de- 

 sired points are apparent and predominant ; in 

 the seed-bed, by rigidly destroying all plants 

 which do not show some desirable variation, 

 breeding in and in from these with strict selec- 

 tion of the most variant form in the particular 

 line or lines, until it becomes fixed by heredity, 

 and as difi'erent from the primal stock as the con- 

 ditions of the case allow. lu nature, the anal- 

 ogous selection, through innumerable genera- 

 tions of the exceedingly small percentage of in- 

 dividuals (as ova or seeds) which ordinarily are 

 to survive and propagate, is made by competi- 

 tion for food or room, the attacks of animals, 

 the vicissitudes of climates, and, in fine, by all 

 the manifold conditions to which they are ex- 

 posed. In the struggle for life to which they are 

 thus inevitably exposed, only the individuals 

 best adapted to the circumstances can survive 

 to maturity and propagate their like. This sur- 

 vival of the fittest, metaphorically expressed by 

 the phrase natural selection, is, in fact, the de- 

 struction of all weaker competitors, or of all 

 which, however they might be favored by other 

 conditions, are not the most favored under the 

 actual circumstances. But seedlings, varying, 

 some in one direction and some in another, are 

 thereby adapted to diflferent conditions, some to 

 one kind of soil and exposure, some to another, 

 thus lessening the competition between the two 

 most divergent forms, and favoring their preser- 

 vation and further separation, while the inter- 

 mediate forms perish. Thus an ancestral type 

 would become diversified into races and species. 

 Earlier variation, under terrestrial changes and 

 vicissitudes, prolonged and various in geologi- 

 cal times since the appearanceof the main types 

 of vegetation, and the attendant extinctions, are 

 held to account for genera, tribes, orders, etc., 

 and to explain their actual affinities. Aflinity 

 under this view is consanguinity; and classi- 

 fication, so far as it is natural, expresses real 

 relationship. Classes, orders, tribes, etc., are 

 the earlier or main and successful branches of 

 the genealogical tree, genera are later branches, 

 species the latest definitely developed ramifica- 

 tions, varieties the developing buds. Briefly : 

 Taken as a working hypothesis, the doctrine of 

 the derivation of species serves well for the co- 

 ordination of all the facts in botany, and afi^ords a 

 probable and reasonable answer to a long series 

 of questions which, without it, are totally unan- 

 swerable. It is supported by vegetable paleon- 

 tology, which assures us that the plauts of the 



later geological periods are the ancestors of the 

 actual flora of the world. In accordance with it 

 we may explain in a good degree the present 

 distribution of species and other groups over 

 the world. It explains, by inheritance, the ex- 

 istence of functiouless parts, throws light upou 

 the anomalies of parasitic plants, and, indeed, 

 illuminates the whole field of morphology with 

 which this volume has been occupied. 



In looking through Part I. we are struck 

 by the many new illustrations, and the new 

 headings of pages and sections, all bearing 

 witness lo the recent rapid growth of mor- 

 phological science. There is an entire sec- 

 tion of nearly thirty pages given to the sub- 

 ject of " Adaptations for Intercrossing" — a 

 subject the interest in which began in 1862, 

 with the publication of Darwin's book on the 

 fertilization of orchids by the aid of insects. 



But, important and interesting as is the 

 volume before us, and rejoicing as we do in 

 the promise of those to come, we are chiefly 

 glad that Professor Gray has proceeded upon 

 the method of putting structural botany first 

 in this elaborate course of study. It is 

 now possible in some of the schools to 

 study living plants, and this' arrangement 

 is an assurance that students of Gray's Bot- 

 any will rationally pursue the subject of 

 classification. 



A Treatise on Hygiene and Public Health. 

 Edited by Albert Buck, M. D. In Two 

 Volumes. Illusti-ated. New York: 

 William Wood & Co. Pp. 1450. Price, 



There is something ludicrous and pitia- 

 ble in the estimates which men form of the 

 relative importance of difi'erent subjects of 

 thought. It seems to be still the law that 

 the popular solicitudes are in inverse ratio 

 to the vital usefulness of the questions to 

 which they are directed. Men lash them- 

 selves into furious excitement over the dif- 

 ferences between tweedledum and tweedle- 

 dee in politics, while they can be aroused to 

 only a languid and careless attention to the 

 life-and-deatb interests of daily family life. 

 Say what we will, the next great subject in 

 order in the development of civilization is 

 that of hygiene. To use this world rightly, 

 and get the most out of it, health is the first 

 condition, and there is no interest so impor- 

 tant both to the individual and to the com- 

 munity as its promotion and preservation. 

 But to accomplish these objects knowledge 



