DECEMBER 4, 1913] 
in connecting facts and in leading to the discovery of 
new facts; and my objection to the conception of 
entelechy is not that it is idealistic, but that it is 
barren. f 
Prof. Driesch now candidly admits that if he had 
only eggs like those of Ascidians and Ctenophores to 
deal with the theory of organ-forming substances 
might suffice, but that in order to account for what 
he calls a “‘ harmonious-equipotential system,” and for 
what I call an undifferentiated tvne of egg (or bud) 
an entelechy must be postulated. Now if the inver- 
sion of the two-celled stage in the development of the 
frog’s egg will produce such a rearrangement of 
materials that two embryos and not one result, is it 
not just possible that the closing up of a fragment 
of a blastula of Echinus may lead, under the stress 
of forces which we may picture to ourselves as surface 
tension, &c., to such a rearrangement of materials as 
may issue in a perfect larva of reduced size instead of 
in a half larva? That organ-forming substances 
limited to special regions do exist in the later embryo 
of Echinus Prof. Driesch has himself shown in one 
of the most exquisite of his earlier researches. At 
any rate, if we adopt this hypothesis we shall be 
urged on to further researches as to the conditions 
of this rearrangement, whereas if we adopt the 
theory of an entelechy about the ideas or methods of 
working of which we know nothing, all future research 
is stopped. : 
The eggs of Asteroids and Echinoids show great 
resemblances in their earlier stages of development 
coupled with subsequent divergences. On Prof. 
Driesch’s theory these divergences are due to differ- 
ences in the indwelling types of entelechy, and no 
further explanation is possible. But when Prof. 
Driesch’s friend and colleague, Prof. Herbst, shows 
that an Asteroid egg can be made to develop into 
something like the Echinoid blastula by immersing it 
in a solution of KCNS, then we are led to speculate 
as to the nature and origin of the chemical differences 
between these two types of egg, which cause the 
differences in their development. 
Prof. Driesch refers to the case of the physicist who 
selects “‘pure material’ for his experiments. I may 
reply by citing the case of the physiologist who in 
investigating nervous phenomena, chooses clearly 
differentiated nerve for his material, and would never 
dream of beginning by examining the phenomena of 
conduction in Amceba. I contend that eggs with 
organ-forming substances definitely localised are far 
“purer material’ for the analysis of the forces of 
development than the undifferentiated eggs of 
Echinus. E. W. MacBripe. 
Imperial College of Science, November 15. 
The Kathode Svectrum of Helium. 
\ NUMBER of articles have recently appeared in 
scientific journals dealing with a spectrum frequently 
associated with the spectrum of helium and by some 
attributed to impurities in the helium. A few words 
relative to this interesting and very beautiful spectrum 
will, I think, clear up the question of the source of 
the spectrum. 
If a helium tube be prepared with disc electrodes, 
carefully freed from impurities, and operated on a 
transformer or continuous current (not on an induc- 
tion-coil discharge), the region about the kathode will 
be filled with a bright pink glow. The spectrum of 
this kathode glow is the spectrum in question. It 
is simply the kathode spectrum of pure helium. If 
care be taken to avoid stray light from the anode 
column it may be obtained quite free from the 
ordinary (anode) spectrum of helium. | When the 
disruptive discharge from an induction coil is used 
NO. 2301, VOL. 92] 
NATURE 
‘to a bright pink. 
401 
to excite the tube or the tube is viewed end on 
through a cylindrical electrode, the two spectra appear 
mixed in various proportions. 
During the writer’s several years of work at the 
Bureau of Standards on the helium tube as a primary 
light standard, scores of helium tubes were prepared 
and operated as above described. It was noted that 
the kathode glow was pale and greyish until the last 
traces of impurities has disappeared, when it turned 
In fact, the appearance of the 
kathode glow is an infallible criterion for the purity 
of the helium, a spectroscope being unnecessary. The 
kathode spectrum of helium, viewed witha large, high 
intensity spectroscope, will be recalled by many who 
have visited the bureau during the last four years. 
Goldstein’s spectrogram reproduced in the Physika- 
lische Zeitschrift, July 15, 1913, is a very good one 
considering the photographic difficulties. 
It is well known that most gases exhibit two and 
a few three quite distinct spectra. These are the 
anode (primary) and kathode spectra, and the 
secondary spectrum obtained with a disruptive dis- 
charge. Nitrogen is a familiar example of a gas 
having all three spectra. Helium is one of the few 
gases and vapours the primary and secondary spectra 
of which are alike, but the anode and kathode spectra 
of which are quite different. P. G. Nuttine. 
Rochester, N.Y., November 7. 
Observation of the Separation of Spectral Lines by an 
Electric Field. 
Tue effect of the electric field upon spectral lines 
is a problem which has caused much discussion with- 
out being solved by experiment until to-day. Applying a 
very intense electric field in an incandescent gas, and 
using suitable optical arrangements, I succeeded in 
separating several spectral lines into components. 
These are polarised rectilinearly in relation to the 
axis of the electric field in the transversal effect 
(radius of vision normal to the electric field). With 
the dispersion used, the hydrogen lines H8 and Hy 
are resolved by the electric field into five components. 
The three located in the middle are in electric oscilla- 
tion normally to the electric field, the two outer ones 
parallel to it. My first paper on the new pheno- 
menon will soon be published in the Berichte der 
Berliner Akademie der Wissenschaften. 
J. STark. 
Aachen, Technischen Hochschule, November 21. 
Phosphorescence of Mercury Vapour. 
Last July I published in the Proceedings of the 
Royal Society an account of a persistent fluorescence 
of mercury vapour produced by excitation of > 2ha05. 
light, obtained from a quartz-mercury arc lamp. I 
have recently placed the fluorescent vapour in a strong 
magnetic field, and find that when the mercury lamp 
is cooled and consequently the ‘'2536” line is sharp, 
the magnetic field increases the intensity of the 
fluorescence several times. If the lamp is allowed to 
warm up so that the ‘2536"’ line becomes broadened 
and reversed, the opposite effect is obtained, i.e. the 
phosphorescence decreases in intensity with the field. 
In this latter case the field strength that produces the 
greatest diminution in intensity increases with the 
temperature of the quartz-mercury lamp. The ordinary 
fluorescence produced by the light from the cadmium 
spark is not affected by the magnetic field. I am at 
present working with the idea of obtaining a satis- 
factory explanation of the persistent fluorescence and 
the various phenomena connected with it. 
F. S. Puivurps. 
Imperial College of Science and Technology, 
November 24. 
