-Erreer oF Haze oN Soar Rotation _MEasuRES.— 
_ The extensive determinations of the sun’s rotation 
which have been made by the spectroscopic method 
have shown remarkable variations, even among results 
obtained at the same observatory at different times. 
Thus the values for the equatorial velocity range from 
1-86 to 211 km. per sec., and observers have not 
agreed as to the inequality of the values obtained -from 
’ different lines at the same time. Again, while some 
observers have found values of the rate of rotation 
progressively increasing with the wave-length, many 
other observations have not shown this effect. A valu- 
able contribution towards tracing the source of such 
discordances has been made by R. E. De Lury, of the 
Dominion Observatory, Ottawa, in a careful investiga- 
tion of the effects of haze on the spectroscopic measure- 
ments (Journ. R.A.S. Canada, vol. x., p. 345). The 
efiect of terrestrial atmospheric haze is obviously to 
superpose a weakened solar spectrum, coming mainly 
from the centre of the sun’s disc and showing no dis- 
placements at all, upon the limb spectra. The 
measured displacements of the blended lines at the 
limb would then be too small, and would vary from 
line to line, according to the character of the line at 
the limb as compared with the centre. Correction for 
the haze effect can be made by correlating accurate 
determinations of the relative strengths of haze and 
limb spectrum with displacements of groups of 
lines of different intensities. 
may be necessary, but Mr. De Lury appears to be 
already convinced that variations hitherto ascribed to 
the sun are mainly due to variations in haze. 
Tue Masses or Visuat Binary Stars.—Mr. R.T. A. 
Innes has been led to some remarkable conclusions by 
a discussion of data relating to binary stars (South 
African Journ, Sci., vol. xii.,,p. 453). All close pairs 
of stars, with few exceptions, are apparently to be 
regarded as binaries, whether they show relative 
motion or not. On the assumption that a binary has 
the same brightness as the sun, Mr. Innes calculates 
its distance from the apparent magnitude, and thence 
the mass, if the period be known. When no orbit has 
been computed, he proceeds in a similar manner, and 
calculates the annual angular motion at the distance 
of the companion which would be produced if the 
primary had the same mass as the sun. The calcu- 
lated motion is mostly much in excess of that observed, 
and Mr. Innes concludes that very few double stars 
have a mass, or ‘'gravitative power,” as he prefers 
to call it, equal to that of the sun. He has been led 
to suppose that gravitative power is small in stars of 
types B and A, moderate in F, and large in G and K 
stars; in types Oe and M it appears to be absent alto- 
gether. The A type is considered to be poorly repre- 
sented among binaries, because stars of this class have 
but little effective gravitative power, notwithstanding 
their great brilliancy. There appears to be a limiting 
distance below which double stars cannot exist, and 
for solar-type stars this is apparently about five times 
the earth’s distance from the sun. It is suggested that 
light-pressure may partly or wholly neutralise gravi- 
tative power in stars of small density and great 
luminosity. 
MUTATION AND EVOLUTION. 
%OF. ARTHUR DENDY’S presidential address, 
delivered in February last, before the members of 
the Quekett Microscopical Club appears in the journal 
of the club for April, and will probably be much dis- 
cussed, inasmuch as it is devoted to an analysis of 
the relation of mutation to the evolution theory, 
the arguments being based on data drawn from the 
sponges. The phenomena of mutation, it is con- 
NO. 2449, VOL. 98] 
Further investigations. 
NATURE 
99 
tended, is more a chemico-physical than a bio‘ogical 
phenomenon. Mutations, such as are observable in. 
sponge spicules, in his opinion, strongly suggest the 
existence of definite factors in the germ plasm. The 
factorial hypothesis, he considers, is further supported 
by evidence which is accumulating as to the general 
course of evolution followed by the Tetraxonida. On 
the whole this evolution seems to have been progressive,. 
accompanied by increasing complexity ot , structure, 
manifested especially in the skeleton, Along certain 
lines of descent, however, it appears that the cul- 
minating point has been passed, and regressive evolu- 
tion is taking place, resulting in simplification of 
structure, by the dropping out of certain types of 
spicule. This loss cannot be regarded as an adaptive 
modification, nor can it be explained as due to 
mechanical necessities. Prof. Dendy concludes, there- 
fore, that it is due to some change in the germ-plasm, 
affecting the power of the sponge to produce the par- 
ticular spicules in question, 
How can we reconcile these facts, it is asked, with 
the belief that evolution has taken place, in the main, 
by slow, successive modifications, rather than by 
sudden mutations? The conception of factors is inti- 
mately bound up with that of mutations, and the 
existence of the one wou'd seem to imply the occur- 
rence of the other. 
As to which set of characters is to be regarded as 
the more important from the point of view of the 
student of progressive evolution Prof. Dendy holds 
there can be little doubt, but how far the division 
into adaptive and non-adaptive corresponds to the 
distinction between fluctuating variation and mutation 
is a different question. Certainly the chances are 
greatly against a mutation, when it first appears, having 
any adaptive significance. The evidence seems to him 
to show that the slow, successive variations of the 
Darwinian theory have had far more to do with the 
evolution of sponges than the process of mutation, 
and are mainly responsible, under the guidance of 
natural selection, for adaptive modifications. 
It is not easy to follow Prof. Dendy in his attempt 
to discriminate between, and apportion the value of, 
adaptive and non-adaptive characters. It would seem, 
however, that he would regard the former as directly 
affecting viability, in proportion to their responsive- 
ness to the demands of natural selection. They are 
characters which are of necessity immediately and 
continuously functional. The latter seem to be re- 
garded as accretions or fortuitous variations, tolerated 
until they acquire survival value—that is to say, until 
they come under the sway of natural selection. If 
this is so, then all non-adaptive characters are poten- 
tially adaptive. They afford the basis for further 
evolutionary phases, or, in other words, the material 
which will determine the trend of future development 
and the fate of the organism for good or ill. 
W.. .Pic Be 
SOME PROBLEMS IN EUGENICS. 
TUDENTS of human heredity from the sociological 
point of view are indebted to the American 
Eugenics Record Office (Long Island, N.Y.). Its last- 
issued Bulletin (No. 15) contains the study of a family 
indicated by the pseudonym of ‘Dack,” showing 
markedly a “hereditary lack of emotional control.” 
The author of the bulletin is Mrs. A. W. Finlay- 
son, and Prof. C. B. Davenport contributes a preface 
in which he emphasises the importance of such 
“eugenics field-work.’’ Mrs. Finlayson has collected 
data with regard to 150 descendants of the pair of 
“Dacks ” who emigrated from Ireland to Pennsylvania 
