ApriL 8, 1915] 
NATURE 
E59 

information under this head afforded by the present 
publication has been common knowledge amongst all 
those interested for so long that it no longer presents 
any features capable of attracting attention. 
The most interesting portion of the present report is 
accordingly that portion that deals with the labour 
employed in the world’s mineral industry. It is shown 
that the number of persons engaged in this industry 
exceeded 6} millions, more than one-third of whom 
were employed in the British Empire. It is interest- 
ing to note that more than one-half of this number 
was employed in coal mining, and as coal mining in 
different countries is more readily comparable than 
any other class of mining, because the conditions 
under which it is carried on present closer points of 
agreement, it may be profitable to compare briefly 
the labour statistics. Out of a total vroduction of 
1,250,000,000 metric tons of coal in the whole world, 
Great Britain alone produces 264,600,000 tons and 
the whole British Empire 314,500,000 tons, or about 
a quarter of the whole output. The other large pro- 
ducers are the United States with 484,900,000 metric 
tons; the German Empire, 255,800,000; Austria- 
Hungary, 51,700,000; France, 41,100,000; Russia, 
= J 7 ~ ’ 
31,300,000 ; Belgium, 23,000,000 ; and Japan, 
19,700,000. It is curious to note that, with the excep- 
tion of the United States, this list includes all the 
important nations engaged in the present war. The 
producing capacity of the miners engaged in this 
industry in metric tons per worker per annum is 
shown in the following table -— 
Great Britain 230 United States 671 
Australia ... .- 535) German’ Empire... 272 
Canada 486 Austria 307 
India 08 129 France 307 
New Zealand . 511 | Russia 142 
South Africa .- 347 | Belgium 157 
Japan 129 
It will be seen that with the exception of India, 
where the labour is almost exclusively native, no part 
of the British Empire can show so low an output 
per head as does Great Britain itself, whilst of 
foreign countries it is only the smaller producers that 
rank worse than ourselves. In part, this small pro- 
duction is no doubt due to the fact that so many of 
our thicker and more easily wrought seams are to a 
large extent worked out, and that we are therefore 
compelled to work the thinner seams, from which a 
smaller output per man is necessarily produced. This 
drawback should, however, have been largely offset 
by the use of mechanical means for cutting and trans- 
porting coal, and it is difficult to avoid the con- 
clusion that the low output is due to the restrictive 
policy covertly, if not overtly, encouraged by the 
Trades Unions. 
It is some satisfaction to find that British coal 
mining is conducted with a great regard for the safety 
of the men engaged in this occupation. The death- 
rate per thousand workers employed is given as 
follows :— 
Great Britain 117 | France 1°49 
British Empire ... 1°24] Russia 4/27 
United States 3°26] Belgium 100 
German Empire... 2°44 | Japan 5/64 
Austria 1°48 
If the death-rate be compared, not per worker but 
per million tons of output, Great Britain will not 
appear in quite so highly favourable a light as com- 
pared with the United States, for example, that of 
the former being 4:66 deaths per million metric tons, 
and of the latter 5°44. Nevertheless, from every point 
of view our standard of safety may be looked upon 
as high. 
NO 237, VOLS] 

It ought to be added that the above statements are 
calculated from the data tabulated in the report in 
question, which gives the figures for the various 
countries as though they were obtained in the same 
way, and therefore strictly comparable, which is far 
from actually being the case. Different countries use 
different methods of determining their mineral pro- 
duction, the number of men engaged in the industry 
and the number of deaths due to it, and the figures 
given are not therefore strictly comparable, though 
they may be expected to give a rough standard of 
comparison. One of the objects aimed at for many 
years by statisticians interested in mineral produc- 
tion was to get an international understanding as to 
the basis on which all these figures were to be deter- 
mined, but now that Germany has in a few months 
destroyed the work of many years of European civilisa- 
tion, and by her own relapse into barbarism has 
dragged all other nations down with her, any prospect 
of agreement on such minor international questions 
appears to be quite hopeless. FS Te: 
REPRODUCTION AND HEREDITY. 
ROF, J. A. DETLEFSEN (University of Illinois) 
has made an important contribution to our 
knowledge of ‘Mendelian’ inheritance by his 
“Genetic Studies on a Cavy Species Cross ’’ (Carnegie 
Institution, Publication No. 205, 1914). The research 
—begun by Prof. W. E. Castle—is of interest as 
affording information from the crossing of two dis- 
tinct species, for the wild Brazilian cavy (Cavia 
rufescens) is apparently sharply distinct from the 
common domestic guinea-pig (C. porcellus). The 
sterility of hybrid animals is known to be a rule 
admitting of many exceptions. In the experiments with 
cavies here described, crosses between C. rufescens 
males and C. porcellus females gave completely sterile 
male and fertile female hybrids. By mating the 
female hybrids with porcellus males, quarter-wild 
hybrids were obtained, again sterile males and fertile 
females; but by repeated back-crosses of female 
hybrids to porcellus males, individuals with increasing 
fertility were obtained. ‘‘ Fertility seemed to act like 
a very complex recessive character; for the results 
obtained were what one would expect if a number of 
dominant factors for sterility were involved, the 
elimination of which would give a recessive fertile 
type.’’ The paper is noteworthy because skeletal char- 
acters of the parents and hybrids are figured and com- 
pared, in addition to the usual external features, such 
as coat-colour, — 
A case of sex-limited inheritance in plants is dis- 
cussed by Mr. G. H. Shull, who has made crosses 
between the typical Lychnis dioica and its variety 
angustifolia (Zeitschr f. indukt. Abstammungs u. 
Vererbungslehre, xii., 5, 1914). The narrow-leafed 
form is a recessive which reappears in half the males 
of the F, generation. All the F, broad-leafed males 
are heterozygous for the broad-leaf factor, while of 
the females half are heterozygous, half homozygous 
for this factor. As regards sex, the female Lychnis 
- is a homozygote and the male a heterozygote. 
Dr. Raymond Pearl continues his observations on 
the reproductive organs of domestic fowls. In a paper 
on the effects of ‘‘ Ligation, Section, or Removal of the 
Oviduct ” (Journ. Exper. Zoo., xvii., 3, 1914), he 
states that these operations have no injurious effect on 
the growth of the ovary, and that after removal or 
closing of the oviducal funnel, eggs are passed into 
the body-cavity, where, if not absorbed at the peri- 
toneal surface, they may cause ‘‘serious metabolic 
disturbances.” In the Journ. Biol. Chemistry (xix., 
2, 1914) Dr. Pearl informs us that injection of the 
