50 



NATURE 



[May 20, 1897 



characters through selection by the mere persistence or 

 survival of residues. If the process of selection continues, 

 the system will ultimately disappear altogether. In the 

 case of selection with renewal the system does not 

 undergo extinction, and, therefore, this is regarded as the 

 more general case, since selection without renewal may 

 be regarded as the limiting case in which the number of 

 renewals is always equal to zero. The consideration of 

 the mode of renewal lay the origination of new objects 

 within the system is followed by a mathematical dis- 

 cussion extending over several pages, and leading to a 

 further elaboration of the idea of selection. 



The idea of adaptation in the abstract is next discussed, 

 and the conclusion arrived at is that between an object 

 and its environment there may be three kinds of adap- 

 tation ; viz. by a modification of the object itself to an 

 unchangeable environment, by a modification of the 

 environment by an unchangeable object, and by mutual 

 adaptability when both are changeable. Following this, 

 there is a discussion of certain special cases of the 

 abstract theory of selection, and some very suggestive 

 observations are made with respect to the difference 

 between selection dtie to mere survival, and selection 

 due to survival accompanied by actual picking out. The 

 point is a fine one, but it appears to be philosophically 

 sound ; and the author introduces a term to express the 

 latter, which might be conveniently translated into 

 "progressive" {Jorischreitende) selection. A mathe- 

 matical appendix to Chapter ii. discusses the relations 

 between the three magnitudes : (i) the number of objects 

 present at a given period of time ; (2) the number of 

 renewals ; and (3) the number of extinctions, on the 

 assumption that the number of renewals is determined by 

 the number of objects already present. 



The concluding chapter deals with the limitations of 

 the principle of selection and its consequences, and the 

 introduction of the abstract results into concrete cases. 

 Most instructive is the section in which the author points 

 out the inapplicability of the principle of selection which 

 governs the organic world to inorganic nature, such as the 

 development of astronomical systems or to the formation 

 of chemical compounds. The author deals very severely 

 here with Carl du Prel, who appears to be responsible for 

 an attempt to introduce the idea of the struggle for 

 existence into the formation of the heavenly bodies. One 

 of the main contentions of the present essay is, in fact, 

 that while the organic world is entirely governed by the 

 principle of progressive selection, the evolution of in- 

 organic nature can be referred to no such principle. 



The essay, of which a very brief account has now been 

 given, will find a place in the literature of the philosophy 

 of evolution. It deals with the question only on very 

 broad grounds, and does not appeal, therefore, to special 

 schools of evolutionists, or to special biological creeds 

 beyond the school of pure selectionists. In this principle 

 of selection the author sees a universal law of develop- 

 ment for organic nature, which can be made the basis of 

 a positive philosophy of evolution. He recognises the 

 part played by Herbert Spencer, although reserving to 

 himself the right of being sceptical with respect to 

 Spencer's developmental machinery. Dr. Unbehaun's 

 position is, perhaps, best defined as an attempt to re- 

 cast the " Synthetic Philosophy " on purely Darwinian 

 NO. 1438, VOL. 56] 



principles. It must be borne in mind that, in commending 

 the work to the notice of English readers, we have not 

 the scientific specialist in view. There is no new dis- 

 covery of fact announced, and most of the principles are 

 already familiar to English students of evolution. The 

 essay is a contribution to philosophy rather than to 

 science. It is the mode of treatment— the manner of 

 presenting the case — that constitutes the chief value of 

 the essay. The endeavour to formulate the principles of 

 selection in exact terms capable of mathematical ex- 

 pression is being made from many sides, and, as a method 

 of attacking such questions, has for some time found 

 favour in this country. It is somewhat surprising, how- 

 ever, to find that no reference is made by the author to 

 the work of Francis Galton and Prof. Karl Pearson, who 

 have done more in this direction than any other writers. 



R. Meldola. 



ILL US TRA TED HIS TO LOG V. 



A Text -book of Histology : Descriptive and Practical, 

 For the use of Students. By Arthur Clarkson, M.B., 

 C.M.Edin. Pp. xx-l-554; with 174 original coloured 

 illustrations. (Bristol : John Wright and Co. London: 

 Simpkin, Marshall, Hamilton, Kent, and Co., Ltd., 

 1896.) 



A BOOK which is illustrated in so lavish a manner 

 as the one before us, is calculated to catch the 

 eye ; but it must also bear the test of critical examin- 

 ation. By its coloured representations of the tissues, 

 it challenges comparison with the well-known " Atlas of 

 Histology " of Klein and Noble Smith, which was pub- 

 lished some seventeen years back. Except, however, 

 that it is smaller and less costly, it suffers grievously 

 by the comparison. Klein's '' Atlas " contained accurate 

 representations made from preparations which were 

 thoroughly up to date, and their description included 

 much that was at that time new; so that the whole work 

 had an unmistakable air of originality, and has re- 

 mained of permanent value. The book before us has 

 pictures which are pretty, as far as gaudy colouring can 

 make them so, but which are, many of them, sadly 

 lacking in accuracy of detail, or have been made from 

 preparations fixed by imperfect methods. The very first 

 figures we come to in the book furnish an illustration of 

 this statement. In the representation of the stages of 

 karyokinesis, the monaster stage is shown with nine 

 chromosomes, each splitting into two. In a succeeding 

 figure of the same stage their number is reduced to 

 eight, and in the following two figures, representing the 

 stage of metakinesis of the nucleus, we find, respectively, 

 eight and ten chromosomes instead of eighteen in each ! 

 Then, again, in such a simple figure as the repre- 

 sentation of human blood-corpuscles a spherical white 

 corpuscle is represented of, at least, twice the diameter 

 of the red corpuscles ; while in the drawing of newt's 

 blood, amongst a number of distorted red corpuscles, and 

 some impossible white cells and blood platelets, a non- 

 nucleated fragment of a white corpuscle is inserted, as if 

 it were a normal constituent 1 The author expresses his 

 obligations to Prof. Rutherford for having taught him 

 the art of constructing histological diagrams. We 



