AUGUST 19, 1915] 
NATURE 
669 

produced and amply illustrated, though the nature 
of the material is against some of the photo- 
graphs being very illuminating. 
In writing this book Dr. Gates evidently had 
a thesis which he was anxious to prove. He 
wishes to show that the various forms known as 
mutants, which are constantly thrown by many 
varieties of Cinothera, cannot be regarded as the 
outcome of any process of Mendelian segrega- 
tion, but that they are due to some other process 
of germinal rearrangement which is termed 
mutation. Mendelian segregation, as is well 
known, is an orderly phenomenon enabling us 
to predict the gametic output of an individual 
formed by the fusion of two gametes of different 
genetic properties. We gather Dr. Gates’s con- 
tention to be that, because in most cases it has 
not been found possible to predict the various 
CEnothera forms arising from a cross, the ordin- 
ary rules of segregation do not apply, and that 
these forms owe their origin to some process 
not yet understood. i 
The explanation of this process of mutation is 
considered by Dr. Gates to reside probably in 
abnormal divisions of the chromosomes following 
upon the loss of some hypothetical ‘condition 
of balance.” He attempts to draw a sharp 
distinction between this process of mutation and 
what he terms the Mendelian hypothesis of muta- 
tion, by which the new form originates through 
the loss (or possibly also by the addition) of a 
definite factor or factors. His point of view is 
not easy to grasp, and perhaps may be best 
illustrated by some of his experiments. In a 
culture of rubrinervis some years ago there 
appeared a new type which he called rubricalyx. 
This form behaves as a simple dominant to 
vubrinervis, and we suppose that Dr. Gates would 
say that on the Mendelian hypothesis of mutation 
it arose through the addition of a factor R. 
When rubricalyx was crossed by grandiflora 
(pp. 254-9), a green-budded form, it gave an Fy 
generation with red buds, though not so red as in 
rubricalyx. In ten different F, families the pro- 
portion of reds to greens varied greatly, being in 
one case as high as 33:1, and in another as low 
as 3:1. In a number of Fs; families similar 
ratios of reds and greens were obtained, while it 
was shown also that some reds bred true to red, 
and that green gave nothing but green. Further, 
there were several cases of an intermediate red 
breeding here. Dr. Gates argues that the 
different ratios of reds to greens and the fact of 
intermediates breeding true negative any Men- 
delian interpretation. Nevertheless the data as 
given present so many features in common with 
cases where a Mendelian interpretation has proved 
NO. 2390, VOL. 95] 


adequate that we feel little doubt that, had the 
analysis proceeded further, an interpretation in 
terms of a few factors would have been forth- 
coming, and we cannot but regret that this pro- 
mising series of experiments should have been left 
in so indecisive a state. 
Rigorous genetic analysis, working character by 
character, has yet to be applied to the GEnotheras. 
That it will prove more complicated than in most 
plants there is no question. The work already done 
shows that the Génotheras, like some other plants, 
may present differences in the genetic properties 
of the male and female gametes produced by the 
same plant. They are also characterised by the 
high percentage of bad pollen grains, which may 
mean that some possible combinations are not 
formed. Indeed Renner has recently shown that 
in the ovules, too, there may occur an abortion of 
embryos corresponding to a given class of off- 
spring (cf. Gates, p. 248). Differences in viability, 
as Dr. Gates points out (p. 89) may also char- 
acterise different forms. With all these possible 
sources of complication to be taken into account 
it is not surprising that the genetic behaviour of 
the GEnotheras is still in a state of chaos, and until 
proper methods of analysis have been applied and 
proved definitely to fail, it is surely premature to 
state that the ordinary rule of segregation does 
not occur in this genus. 
In conclusion there are a few small alterations 
which we should like to find in another edition. 
“50” on line 3 of p. 23 should surely be “20 
per cent.,” and to call Drosophila a “ pumice-fly” 
(p. 303) might lead to misapprehension as to the 
manner of its subsistence. We think also that in 
an English book the form Venice is to be pre- 
ferred to Venedig (p. 248). A common error is 
perpetuated in the sentence on p. 320—‘The new 
character is, at least in some cases, a dominant in 
crosses, which accounts for its spreading.” The 
dominant, qua dominance, has, of course, no ad- 
vantage over the recessive in a mixed population. 

EVOLUTION THE OTHER WAY ABOUT. 
Histoire de lU’Involution Naturelle. By E. 
Marconi. Translated from the Italian by M. I. 
Mori-Dupont. Pp. xii+505. (Raris -seeAs 
Maloine, 1915.) Price 15 francs. 
HE evolution-theory aims at formulating the 
Se way in which the present-day state of 
things has come about. It is not demonstrable like 
the law of the conservation of energy; it is a way 
of looking at things—an interpretation. It reads 
the present as the natural outcome of the past. In 
this broad sense Dr. Enrico Marconi might be 
called an eyolutionist, but he refuses the label, 
