Vill 
formula, C,H .0,;, based on this assumption was 
suggested as recently as 1908. 
The view more generally held, however, has 
been that pure gallotannic acid has the composi- 
tion C,,H,,O9, and in constitution is digallic acid, 
the anhydride of gallic acid. Nevertheless, there 
are some facts known which do not altogether 
tally with this view. 
A summary of the present state of our know- 
ledge of the subject is provided by the author in 
the section devoted to the classification and con- 
stitution of natural tannins. This includes an 
account of the recent researches of Nierenstein, 
Ijin, Manning, and others, brought down to the 
year 1910. The first-named investigator concludes 
that ‘‘ tannic acid’’ is a mixture of at least two 
compounds, namely, digallic acid and a “leuco- 
tannic” acid; its composition is therefore more 
complex than has been generally supposed, and the 
question of its exact chemical constitution is still 
an unsettled one. 
On the practical side the recognised processes 
for the detection and estimation of tannins are 
described at length. For the testing of tannin 
materials both the European and the American 
“official ” methods are included. 
The sections on dyestuffs and colouring matters, 
occupying as they do some 550 pages, are the 
chief feature of the volume. Messrs. Dreaper and 
Feilmann deal with dyes and colours generally, 
describing the chemistry and classification of these 
products, and the analysis of colouring materials. 
Professor Hewitt discusses the chemistry of 
special groups of synthetical dyestuffs, and is 
characteristically happy with complicated struc- 
tural formule. Prof. W. M. Gardner is respons- 
ible for the section on the group of natural 
colcuring-matters, which gives a short outline of 
the method of production and chemistry of indigo, 
logwood, iustic, weld, turmeric, gamboge, 
annatto, cochineal, madder, alkanet, and the lac 
dyes. More analytical details would have been 
welcome here, but no doubt the question of space 
had to be considered. A separate section is 
devoted to substances employed for colouring 
foods. Although this could have been incorpor- 
ated with the other chapters on dyes and colour- 
ing-matters, users of the book who have to do 
with foodstuffs will consider the separate treatment 
a decided advantage. 
So many new dyestuffs have been produced in 
recent years that the problem of identifying a 
given colour has become greatly more difficult 
than it was, say, a generation ago. In fact, as 
regards synthetic dyes, the general analyst, as 
distinct from the specialist in colour chemistry, 
must now perforce content himself in many cases 
NO. 2218, VOL. 89] 
Supplement to ‘‘ Nature,” May 2, 1912. 
with assigning a given colour to its generic group. 
The positive recognition of the individual dye, even 
if only one is present, is becoming more and more 
frequently an almost hopeless task when time is 
limited and the operator has no special experience. 
Happily, the general commercial analyst—for 
whom, after all, this work on “commercial organic 
analysis’ is primarily written—does not always 
need to name the precise dye or pigment he may 
meet with in his work. Frequently it will suffice 
to discriminate between a natural and an artificial 
colour, and in the latter case to refer it to its 
class, as, for instance, an azo-compound, a “sul- 
phide” dye, or a diphenyl-methane derivative. But 
when closer differentiation is necessary, there is 
plenty of help for him in this volume. Gos: 
CYTOLOGICAL PROBLEMS. 
Das Problem der Befruchtungsvorginge und 
andere zytologische Fragen. By Prof. B. 
Némec. Pp. iv+532. (Berlin: Gebriider Born- 
traeger, 1910.) Price 20 marks. 
F we had to compress an account of the im- 
pression left by a perusal of Prof. Némec’s 
book into a sentence, it would in effect be that an 
otherwise interesting theme has been damaged 
by undue verbosity. 
The author is well known for his experiments 
on the action of drugs, especially chloral 
hydrate, upon dividing cells, and a great part 
of the treatise before us is devoted to an ex- 
tended account of these investigations. Némec 
believes that one of the actions of such drug's is to 
inhibit the formation of cell walls between the two 
nuclei resulting from a division, and a second, but 
not invariable, consequence lies in the re-fusion 
of the nuclei thus formed. Such double nuclei are 
marked by the large size of the cell, as well as the 
resultant nucleus, whilst the latter contains twice 
the number of chromosomes normally occurring in 
the nuclei of the particular tissue in the untreated 
state. 
In these discoveries he has been confirmed by 
other investigators, but he goes further and con- 
siders that the ‘‘syndiploid” nuclei thus produced 
may (though not necessarily) be reduced to the 
normal diploid type by a process resembling the 
reduction of chromosomes at the meiotic phase of 
the life-history of an animal or plant. In this, 
however, his conclusions are not borne out by the 
researches of other workers who have investi- 
gated the problem in Germany and in this country. 
Other syndiploid cells, instead of reverting to 
the normal type, may be simply killed out and 
leave no further cell products in the ontogeny of 
the organism. 
