tials assumed by the metals, is al- as the result of experiments with hymost exactly the same for all the drogen that electrons of velocity cormetals studied if the metal surfaces responding to 800-volts drop can proare scraped in vacuo. Hughes (Philos. duce singly charged molecules, but Mag., Feb., 1916) has measured the that impact by these molecular ions velocity of the normal and selective is necessary to dissociate the H and electrons, and finds little difference produce Thomson's H, molecule. Furbetween them, indicating that the ther studies of thermonic discharge two effects are not fundamentally dif- have been made by Lester (ibid., ferent. Piersol (Phys. Rev., Sept., March, 1916) and Stoekle (Phys. 1916) has examined the effect of heat- Rev., Nov., 1916) which throw more ing in vacuo on the photo-electric light on the tremendous influence of properties of platinum, palladium and surface conditions. Tolman and other metals, and has developed some Stewart have obtained direct experiunexpected points. Robinson (Philos. mental evidence of the production of Mag., Oct., 1916) continues his work an electromotive force by the accelwith the photo-electric discharge eration of metals, a minute effect refrom very thin platinum films, and quiring the most refined manipulaproves the existence of a very pro- tion for its detection. A popular disnounced maximum current per unit cussion of the modern theories of the absorbed light for a particular thick-electrical properties of metals is ness of film of about 10 cm. The existence of this maximum cannot be considered as due to the maximum of absorption discovered by Partzsch and Hallwachs.

Electricity. Skinner's recent theory of the glow discharge has been subjected to extensive experimental test in recent work by Cheney and by Neuswanger (Phys. Rev., Feb., 1916) and the general results of the theory satisfactorily confirmed. A new method of measuring ionic mobility has been developed by Ratner (Philos. Mag., Nov. 1916) and the results obtained with it which are not in accordance with Wellische's recent theory as to the nature of negative ions.

given by Sir J. J. Thomson in his usual fascinating style in several papers republished in the Scientific American Supplement (April and May, 1916). Data on some of these same complicated electrical properties are given by Wald (Phys. Rev., Feb., 1916) and Smith (ibid., Oct., 1916).

Magnetism.-No very striking development in this field is to be recorded, but it is evident that investigators are finding it difficult to reconcile the Weiss magneton theory of magnetism with experimental results. This is especially the case with the thermo-magnetic data of Honda and Ishiwara, and is in evidence also in the study of the magneto-chemistry of copper salts by Cabrera.

X-Rays. The use of X-rays for crystal analysis according to the method of Bragg is steadily increasing, important work having been done by Vegard (Philos. Mag., Nov., 1916), who, in a study of xenotime and anatase, has reached fairly definite conclusions as to the relation of the oxygen atoms to the metal atoms in the molecule. Ogg and Hopwood have used the method to decide sharp

An extensive study of arcs between high melting-point metal electrodes, especially tungsten, by Makay and Ferguson (Jour. Franklin Inst., Feb., 1916), leads to the conclusion that the (slight) vaporization of the electrodes plays no essential part in the electrical conduction. There are reasons for extending this conclusion to the carbon arc, but Duffield (Proc. Roy. Soc., Dec., 1915) comes to the opposite conclusion, that for very short arcs the vaporization is directly against the proposed crystalloly determined by the current and the ionic charge of carbon.

graphic law of "valency volumes." Bragg (Chem. Soc. Trans., March, Ionization by collision is the sub- 1916) has summarized the results object of several theoretical papers by tained by applying X-ray methods to K. T. Compton (Phys. Rev., April crystal study, and Debye and Shoner and May, 1916), while Dempster (Phys. Zeit., July, 1916) have made (Philos. Mag., May, 1916) concludes a first attempt to obtain information

on the position of the electrons in the atoms by reflecting X-rays from cylinders of amorphous substances.

Dec., 1915), who expose the active material to the impact of a particles from another source, without proOur knowledge of X-ray spectra, ducing any effect. Richards and that is, the wave length of X-rays Wadsworth (Jour. Am. Chem. Soc., produced from the elements when Feb., 1916) have studied with great bombarded by cathode rays, is being exactness ordinary and radioactive continually extended, notably in a se- lead, finding that the density and ries of papers by Siegbahn and his atomic weight are both different for coworkers (Phil. Mag. and Phys. the two kinds of lead, but in such a Zeit.). New lines are being discov- way that the atomic volume is very ered, and by using a vacuum spectro- nearly constant. The electrical charge meter Siegbahn has measured longer of recoil atoms of radium and thoriwave lengths (12.3 A. u.) than any um have been examined by Wertenheretofore noted, except, of course, by stein (Comptes Rendus., Dec., 1915) Sir J. J. Thomson, using his special and Henderson (Nov. Scot. Inst. Sci., methods for obtaining soft (or long Oct., 1915), and it is found that the wave-length) X-rays. A summary of charge depends on the gas or vapor Thomson's work is given in Engineer- present. A new long range a particle ing (April, 1916). The Mosely linear from thorium has been detected by relation between atomic number of Rutherford and Wood (Philos. Mag., the source-element and the square April, 1916), and Biggs (ibid., May, root of frequency of X-rays produced 1916) has brought out the very interturns out to be not generally linear. esting fact that the energy of the The absorption coefficient of soft secondary B-rays is not measurably X-rays has been investigated by Mil- altered by partly absorbing the Xler (Phys. Rev., Oct., 1916), and rays which produced them. A sumBarkla and Shearer came to the rath- mary of the constants of radioactiver surprising conclusion that the Kity is given by Wendt (Phys. Rev., and L X-rays, though of very differ- March, 1916). ent frequency, expel electrons with the same velocity when they produce ionization in a gas. Forman (ibid., Jan., 1916) observes a definite increase in opacity of iron to X-rays, due to magnetization, and Webster's results on the quantum relationships of characteristic X-rays are of decided significance. He finds that none of the K lines in the X-ray spectrum of rhodium is produced until the cathode rays have a velocity sufficient to produce X-rays as short or shorter than the shortest K line. Increase of velocity after this increases the relative intensity of the K lines very rapidly as compared to the general background of rays. Of similar significance is Hull's observation (ibid.) that the maximum energy of the cathode particles is equal to Planck's h times the maximum frequency of the X-rays produced.

Radioactivity.-Many attempts have been made to alter the rate of decay of radioactive substances by changing physical conditions, all of which have led to negative results; perhaps the most searching is that of Danycz and Wertenstein (Comptes Rendus,

Atomic and Molecular Structures.Much of the recent work in light, ionization, radioactivity and X-rays deals so much with questions of atomic and molecular structure that it might well be classified under this heading. There remain to be mentioned only a few articles dealing more exclusively with questions of structure. Parson (Smith. Contrib., Nov., 1915) builds up a theory in which a magneton is the nucleus, but the Bohr type of model, with a small positive nucleus as suggested by Rutherford, receives the most attention. Kossel (Ann. d. Phys., March, 1916) gives further consideration to his modified Bohr structure, which, whatever one may think of its probable reality, embodies better than any other the facts recently discovered about characteristic X-rays. Fajans (Phys. Zeit., Dec., 1915) summarizes recent work bearing on the periodic system, especially with reference to the radioactive elements, and Harkins and Wilson (Philos. Mag., Nov., 1915) discuss structure from the standpoint of energy changes involved in atomic formation.

XXV. THE BIOLOGICAL SCIENCES

ORGANIC EVOLUTION

W. L. TOWER

nection, eugenic discussions and opinions, the suggested methods of treatment of diverse population problems, center more and more about purely biological processes and strikingly less around the different euthenic processes. The European War and the problems of elimination and replacement of losses in belligerent populations, with the array of associated problems both biological and social, naturally have produced an extensive literature, which, unfortunately, is not of any marked value, but is mainly à priori opinion, dogma or propaganda not too well conceived or presented. Little that appears solid or suggestive is to be found in these war eugenic writings, and not a few of them are distinctly hysterical in statement and in language.

General Survey of Activities.-The | the human race. In this latter conyear 1916 shows a marked decrease in activity in evolutionary research, as measured by the output of investigations since the last report. With Europe involved in war and her scientific energies consumed in lines that contribute directly to military necessities of the moment, contributions from European workers are few, and, in the main, are results which were on hand at the beginning of hostilities, new investigations being entirely absent. In the non-belligerent countries, likewise, there is a falling off of the output for the year, in number of publications and in the progress that might be expected therefrom. The general result, therefore, is that the year shows little progress in further development of general theories and concepts, with no distinctly new developments therein, but mainly the production of added data and the elaboration of instances and conditions in the field of organic evolution. Much of the latter type of investigation, however, is distinctly valuable in clarifying previous investigations and ex-tigations, Genetics, began publication tending them, thus providing a basis for more substantial advance in the future.

The chief activities of the year center in or around the Mendelian theory of heredity: in the further investigations of the mechanism of the Mendelian principles, especially in their relations to sex, sex-linked and sexlimited characters; in the conditions of mutation in the Enotherae, and the relations of this phenomenon to Mendelian mechanisms; and, lastly, in the continued and effective application of these newer genetic methods to the problems of improvement in economically valuable plants and animals, as well as to the problems of

Establishments for investigations in organic evolution, as well as resources therefor, remain substantially as in the preceding year, and the number of workers remains about the same. A new journal for the record of inves

during the year and promises to serve a useful purpose in the recording of American investigations (see also Botany, infra). All European journals and publications are diminished in volume and in frequency as also in regularity of issue.

Several books of general interest have appeared during the year. T. H. Morgan in A Critique of the Theory of Evolution, presents an attempt to interpret some of the older evolution data in terms of modern genetic research, with interesting and suggestive results; H. F. Osborn, in Men of the Old Stone Age, gives an admirable account of the early history of man, the remains, art, industries, and the

In

useful surveys of the aspects of the evolution theory with which they are concerned, and in all there is present not a little of the interpretative element, of the attempt to see how far the newly developed concepts fit the observed conditions in nature. general this is a welcome development, and no doubt one that will serve as a valuable corrective and a preventative against expenditure of effort in unproductive directions. At present, however, this interpretation has not progressed sufficiently far to enable us to estimate accurately the general value of the newer developments in evolution hypotheses.

Evolution of Species.-Few attempts to trace the evolutionary history of species are recorded. This is not unexpected, in that most of these histories are the product of European

setting in which primitive man lived as far as known at the present time. M. Grant, in The Passing of a Great Race, attempts to present the picture of European peoples in the period between that covered in Osborn's work and the beginnings of European races as recorded in Ripley's The Races of Europe. Grant's book is not in the same class with that of Osborn or Ripley, although the opportunity was no less. The three, however, present a most attractive history of man in Europe, but are in the main silent, or at best interpretative, as to the methods and factors that were effective in the evolution of the human species. Somewhat in the same line is Huntington's Civilization and Climate in which are presented the author's views of the climatic effects upon the human animal and their role, especially in the development of the diverse as-workers, who are now otherwise enpects of civilization; while many do not agree with the author in his conclusions, still he raises questions that are well worth serious consideration and further investigation. R. Pearl, in Modes of Research in Genetics, gives useful details, formulae and methods for the prosecution of genetic investigations along the most approved lines. J. M. Coulter, in Evolution, Heredity and Eugenics, gives a good elementary presentation of a wide array of topics, for the use of young students especially. The usual crop of texts produced for commercial purposes have appeared during the year, none of which has any special merit or shows any advance over the usual book of this class.

Evolution Hypotheses. Substantially no advances either in the further proof or in the elaboration of evolution hypotheses are found in the records of the year. Surveys of the present conditions of these hypotheses are good and useful, indicating in general an attempt to determine an orientation upon which to base investigations for the future. Of especial merit are Gates' "The Mutation Factor in Evolution"; J. A. Thomson, "Originative Factors in Evolution"; C. B. Davenport, "Evolution Theory in the Light of Modern Genetic Research"; H. H. Bartlett, "Mutation Theory from the Standpoint of Enothera"; all present illuminating and

gaged. The most interesting perhaps is "The Ancestry of the Goose" (Jour. Her.), showing the probable development of the domesticated goose from the wild gray lag goose, found wild over most of the Old World. No evidence, however, as to the methods and factors in this evolution are derived from this study.

Variation and Mutation.-A sharp decline in activities in the fields of variation and mutation is noticeable, even the purely descriptive instances of "variations" of different kinds showing the lowest output in many years. The chief activities in variation center about the question of the action of selection in the alteration of characters. Much discussion between W. E. Castle and others upon this question is found in the journals of the year, but without any conclusive showing, both sides claiming proof more or less emphatically. The same problem also finds complications, not elaborated at present, in the attempted interpretation of some selection effects as due to multiple factors, multiple allelomorphs, and to diverse aspects of the pure-line hypothesis. The new data recorded, while good and carefully obtained, unfortunately are not of such a nature that "interpretation" by hostile "schools" is impossible, and as a result the entire "selection question," in its relation to the value and rôle of small variations in

evolution, is in a highly unsettled condition, with no distinct progress towards solution during the year.

further findings in the grouping of the gametic factors in this animal, in total present the best picture of the mechanism of heredity and behavior of the characters in inheritance that we possess for any organism. Among the publications of the year may be mentioned as of general interest C. B. Bridges' “Non-disjunction and its Bearing upon the Chromosome Theory of Heredity," presenting the general aspects of non-disjunction, and H. J. Muller's "Mechanism of Crossing Over in Drosophila," these two papers pre

H. S. Jennings, in "Variation, Selection and Heredity in Difflugia Corona" (Genetics), presents a continuation of his previous investigations of the same activities in unicellular organisms. He shows that the natural population consists of many hereditarily diverse stocks, and that a single stock, derived by fission from a single individual, gradually differentiated into many hereditarily diverse stocks, showing, he thinks, that selec-senting a good digest of the year's adtion is able to produce marked results. L. M. Standish, "What Is Happening to the Hawthorne?" (Jour. Her.) gives a good brief account of the curious conditions in this plant and of some of the many varieties that have been found; he suggests that the conditions are due to the hybridization of the two species and thinks that the new variants are not new species. O. Koehler ("Ueber die Ursachen der Variabitität bei Gattungsbastarden von Echiniden," Zeit. Ind. Abs. Vererbungslehre), gives interesting data on the variations in the characters of the hybrids in Echinoids. Statistical investigations are very few, because of the preoccupation of European biometricians and the unpopularity of biometrics in America.

vance in this aspect of hereditary behavior. E. M. East records added data in the inheritance of characters in Nicotina; R. H. Biffen, some interesting facts in the suppression of characters in crossing; and in the same line are the findings of G. N. Collins and J. H. Kempton (Jour. Her.) in "Patrogenesis,' a form of heredity in which the female characters are excluded from the hybrid progeny, as shown in the crossing of the grasses Tripsacum and Euchlaena. Just how this occurs is not clear from the evidence presented and may be only one aspect of the so called "somatic segregation," a subject presented in some detail by E. J. Kraus (Jour. Her.).

C. H. Danforth in "Is Twinning Heredity. All activities in the Hereditary?" (Jour. Her.) recites the year in heredity center about aspects probable causes of twinning and gives of the Mendelian theory, and inves- data of the inheritance thereof, which tigators have either abandoned con- seem to indicate an hereditary charsideration of other and older concepts, acter but perhaps not entirely so. In or are too busy reaping the harvests the same class is the study of E. N. to be obtained so readily in the newer Wentworth (Jour. Her.) on the infield. One finds little mention of the heritance of fertility in swine, reachtheory of ancestral influence in hered-ing the conclusion that it is inheritaity or of the neo-Lamarckian princi- ble to a certain extent. J. L. Bonhote, ples and certainly no additional evi- in Vigor and Heredity (London), and dence in their support. The records others give a considerable body of infor 1916 are in the main extensions formation on the inheritance of these of those of the preceding year. physiological characters, especially No distinctly new aspects or concepts those associated with the reproductive are found, and the investigations are process, the determination of the belargely of a routine nature, to deter-havior of which may lead to methods mine the behavior of the pairs of of much value in the production of characters under investigation. Work- domesticated races of high productivers are now engaged in the cataloguity and vigor in the offspring, an acing of the behavior of organic charac- complishment of no little economic ters. The investigations of T. H. Mor- value. gan and his associates, especially of the phenomena of non-disjunction and of crossing over in Drosophila, the

C. R. Stockard (Am. Nat.) in his account and analysis of the inheri tance of degeneracy and deformity in