OUR BOOK SHELF. 
Palacontologie und Descendenzlehre. By E. Koken. 
Pp. 33; illustrated. (Jena: G. Fischer, 1902.) 
IN this essay, read before the Congress of Science and 
Art held at Hamburg in September last, the author 
briefly explains in a popular manner some of the more 
important evidence in favour of evolution afforded by 
paleontological researches and discoveries. After 
alluding to the old belief in the separate creation and 
immutability of species, Dr. Koken mentions Lamarck’s 
theory, and then passes on to the revolution in scientific 
thought and belief brought about by Darwin’s work. 
With a brief reference to Waagen’s investigations and 
theories in regard to the mutations of ammonites, and 
the expression of the belief that what holds good in this 
case will also apply to other groups, he proceeds to cite 
some of the most striking instances of the descent of one 
group from another. In regard to mammals, it is con- 
sidered that the earliest forms were nearly allied to the 
Insectivora, and that from these were developed the 
Creodont Carnivora, from which subsequently branched 
off the placentals on the one hand and the marsupials 
on the other. Allusion is next made to the importance 
of Archzopteryx, as in some respects a connecting link 
between birds and reptiles. Attention is then called to 
the important evidence which has been obtained during 
the last few years as to the relationship between the 
anomodont reptiles and mammals on the one hand, and 
between the former and the labyrinthodont amphibians 
on the other. A wide cleft still, however, separates 
amphibians from fishes—a cleft which, in the author’s 
opinion, is in no wise spanned by the lung-fishes, the 
amphibian resemblances of which he believes to be 
largely adaptive. 
Having cited the foregoing and other instances of 
genetic relationship between various classes, Dr. Koken 
next proceeds to consider numerous cases of inter- 
gradation between minor groups. In the Mammalia he 
first of all refers to the now well-known fact that in the 
early Eocene it is almost impossible to distinguish between 
unguiculates and ungulates, and then proceeds to discuss 
several of the phylogenetic lines into which the latter have 
developed. Special mention is made of the clawed chali- 
cotheroids of the Miocene and Pliocene, as a remarkable 
side-branch of ungulate development ; and Kowalevsky’s 
doctrine of the “adaptive” and “inadaptive” modi- 
fications of the artiodactyle carpus is fully explained. A 
very remarkable instance of the evolution of one type 
from another, which has not received so much attention 
as it deserves, is exemplified among the dinosaurian rep- 
tiles by the Liassic Sce/¢dosaurus and the Upper Jurassic 
Stegosaurus, skeletons of which are figured in juxta- 
position. 
This excellent little sketch concludes with some 
remarks upon former land connections and general 
observations on the evolution of the surface of the 
globe and its inhabitants. Reels 
The Laboratory Companion to Fats and Oils Industries 
By Dr. J. Lewkowitsch, M.A., F.I.C. Pp. xi + 147. 
(London : Macmillan and Co., Ltd., 1901.) Price 6s. net. 
THE book is essentially a collection of tables of the 
numerical values obtained in the analysis of oils and 
fats, and of tables useful in industries where oils and fats 
are employed ; it forms a companion to the author’s 
earlier publication on the ‘‘ Chemical Analysis of Oils, 
Fats and Waxes.” The amount of information in the 
book is very extensive, as may be judged from the fact 
that the number of oils only, for which constants are 
given is 111, and the number of fats 65. 
The author states in his preface that “numerical 
values, so-called constants, and variables, have been 
NO. 1701, VOL. 66] 
NATURE 
[JUNE 5, 1902 
carefully scrutinised, and only the most reliable ones 
have been given. In some cases the most probable 
values had to be decided on.” As the consequence of 
this, we find in the majority of cases single numbers 
given for the iodine value, saponification value, &c., of 
oils and fats. This precludes reference to the results of 
the various observers. The arrangement of materials 
under the heading of separate manufactures is a very 
useful feature. Thus, under the heading “ soap manufac- 
ture,” are eight tables, including such information as the 
percentages of caustic soda and caustic potash in caustic 
lyes, the influence of temperature on the specific gravities 
of caustic soda solutions,'and the amounts of caustic alkali 
solutions required to saponify fats of certain mean 
molecular weights. 
LETTERS TO THE EDITOR. 
(The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejecied 
manuscripts intended for this or any other part of NATUKE, 
No notice ts taken of anonymous communications.| 
Colour-variation in the Guinea-fowl. 
As this bird is such a recent addition to the poultry-yard (for, 
although known to the Romans, it went out of domestication in 
the Middle Ages) and has not been selectively bred by fanciers, 
its spontaneous variations are particularly interesting. Here, in 
India, where guinea-fowls are much bred, several well-defined 
types of coloration constantly present themselves in these birds,. 
kept solely for the table. 
There is first the normal dark-grey form, speckled with white 
and with white bars on the primary quills. This is the 
commonest ; but it varies from the wild type in having more 
white on the naked head and neck, and generally in havifg the 
toes and shanks more or less orange instead of black. 
Secondly, there is a form, marked exactly as the above, but 
ona lavender or French-grey background; it resembles, how- 
ever, the dark normal bird in the coloration of the head and 
legs. 
= third form is of a purplish-slate without spots, but retaining 
the white bars on the primary quills ; the head and legs also are 
coloured as in the common normal form. 
There are also, of course, albino birds, which have entirely 
orange-yellow legs and feet, and no dark purplish hue about the 
bare head, but only white and red. 
The pied birds which occur are particularly interesting, the 
marking being very constant—white underparts and white 
primary quills. The white may invade more of the wing, and 
may be reduced in amount on the breast and wings until the 
coloured form is reached, but I have never seen a splashed or 
blotched bird, such as one often finds among pigeons or ducks. 
All the colours, spotted-grey, spotted-lavender and slate, 
may be pied like this, but the normal spotted-grey oftenest, as 
one would naturally expect from its greater frequency. The 
bare dewlap of these pied birds is white when the white feather- 
ing comes as far, not blue or purple as in coloured birds. 
The only unspotted-lavender bird I have seen as yet wasa 
white-pied one. 
Ihave not had the same opportunities of studying guinea-fowls 
in England as I have out here, but certainly, to the best of my 
recollection, all the colour-types I have described occur there, 
which, considering the difference of climate, shows that this 
factor does not determine variation in this bird. 
As I have remarked above, the pied birds grade into the 
coloured ones; but typical specimens are more common than 
intermediate ones, and there is no gradation whatever between 
the two spotted forms, the dark-grey and lavender. The un- 
spotted slate form does often display a few white-marked body- 
feathers, but by no means tends to intergrade with the normal 
type. 
If this bird, with its uniform body-colour and barred primaries, 
occurred in a wild state, the markings of the quills, concealed as 
these are in repose, would be set down to sexual selection or 
claimed as ‘‘ recognition marks” ; and a similar cause would be 
