JUNE 10, 1915] 
NATURE 
395 

obtained with end-on tubes, from 5 to Io mm.° in 
diameter and about 30 cm. long, with quartz windows, 
and at pressures in the neighbourhood of 5 mm. The 
necessary exposure varies from five minutes to an 
hour, according to the width of the slit, the absorptive 
power of the»medium, etc. I have obtained a beauti- 
ful photograph of the absorption spectrum of benzol 
vapour with fifteen minutes’ exposure. 
E. P. Lewis. 
University of California (Department of Physics), 
Berkeley, California, May 18. 
The Relation between Chromosomes and Sex- 
determination in ‘‘ Abraxas grossulariata.’’ 
In a paper on this subject in the Jowrnal of Genetics 
(vol. iv., June, 1914, p. 1) I gave evidence that in a 
strain of A. grossulariata which I have bred for several 
years two kinds of eggs are produced, having respec- 
tively twenty-eight and twenty-seven chromosomes. 
Since the somatic chromosome-number is fifty-six in 
the male and fifty-five in the female, it seemed evident 
that the eggs with twenty-eight were male-determin- 
ing, those with twenty-seven female-determining. In 
this strain some families in each generation consist 
entirely of females, so it was hoped to prove the cor- 
rectness of the conclusion with regard to sex-deter- 
mination by finding that in families consisting entirely 
of females all the eggs contain twenty-seven chromo- 
somes. I have now examined the eggs of several such 
families, and find, contrary to expectation, that the 
equatorial plate of the inner polar spindle contains 
twenty-eight chromosomes about as frequently as 
twenty-seven. The new material confirms the observa- 
tion that twenty-seven occur in one spindle and twenty- 
eight in the other, but it seems to make it certain that 
the presence of twenty-eight chromosomes in the inner 
spindle does not necessarily cause the production of a 
male—at least, in the strain which produces all-female 
families. A possible explanation of the anomaly is 
that in all-female families a chromosome is eliminated 
at a later stage, but at present I have no direct 
evidence for this. I have material preserved in the 
hope of testing this suggestion, but the investigation is 
likely in any case to be a lengthy one, and circum- 
stances may prevent my continuing it for some 
months. I therefore make this short statement of the 
facts as at present known, in order that it may not be 
assumed that the existence of male- and female-deter- 
mining chromosomes has been finally demonstrated in 
Abraxas. 4 
LEONARD DONCASTER. 
Zoological Laboratory, Cambridge, June 7. 
Cavities due to Pyrites in Magnesium Limestone. 
In some districts it seems that iron pyrites formed 
an important constituent during the deposition of the 
Magnesium Limestone—not only in the north of Eng- 
land, but in America also in some of the Magnesium 
Limestones of the Cambrian age. 
The Durham beds at Fulwell Hill Quarry give us 
ample evidence of this, as regards the English beds, by 
their very numerous cavities, the shape of which, 
which cannot be attributed |to anhydrite, affords the clue. 
Unless carefully sought, the salts of iron are not 
noticed, nor are ferruginous band-stains conspicuous 
or frequent. 
Some years ago I obtained specimens from the 
Roker Cannon-ball bed; some of them, recently placed 
in the Jermyn Street Museum, have been examined 
by Mr. A. F. Hallimond, the assistant-curator, who 
NO. 2380, VOL. 95| 

has labelled them ** pseudomorphous after mispickel.” 
These, however, were formed on the outside of the 
calcareous spheres. I have also secured from the 
Fulwell Hill Quarry a few specimens of the concre- 
tionary structure with cavities containing limonite in 
powder. There are, however, a large number of 
empty cavities that apparently once contained pyrites, 
which are free : 
from the prevalent 
““marl’’ powder, 
from dolomite, or 
from any traces 
of anhydrite. 
They are from 
about 4 in. up to 
about 6 in. in 
diameter, are 
roughly spherical, 
but with project- 
ing cones; they 
are often  decor- 
ated with strings 
of white calcite, 
though occasion- 
ally they are iron- 
st aim ed (See 
Fig. 1). xh. 
Rarely, more or 
less solid  speci- 
mens are met 
with (Fig. 2) 
which are casts 
of similar cavities, 
due to the deposit 
in them of cal- 
cium carbonate. 
Drea |ileister, eon 
the Technical In- 
stitute, Tunbridge 
Wells, has kindly 
examined these for 
me, and has found 
them to contain a 
notable amount of 
calcium fluoride, 
which, so far as I 
am aware, is a 
new observation. 
-Other kinds of cavities are occasionally met with 
in the concretions of these beds, but, except the so- 
called cells, there are no others of frequent occur- 
rence, while these, to which I am directing attention, 
are found in all the beds, both of limestone and marl. 
I have seen no traces of copper. 


Fic. 2.—Calcite cast of a cavity probably after 
FeS2. xX}. 
GEORGE ABBOTT. 
2 Rusthall Park, Tunbridge Wells, May 12. 

POISONOUS GASES IN WARFARE 
THEIR ANTIDOTES. 
1 the Concise Oxford Dictionary a ‘ Stink- 
ball” is defined as “a vessel containing 
explosives, etc., generating noxious vapours, used 
formerly in naval warfare and still by Eastern 
pirates.” The Germans have shown the world 
how science may be degraded in its application 
to the purposes of the pirate, and our military 
commanders have now to deal with a new weapon 
previously unheard of in the field. Steps have 
already been taken to provide protection for our 
men, but a survey of the whole question of the 
composition and the properties of the gases which 
AND 
