242 
NATURE 
[May 7, 1914 
tion is only about 3 per cent. greater than that of the 
exciting one, and is about inversely proportional to 
the sixth power of the atomic number, we get 
Vv =2-23 x 10°(M—1) cm./sec., while Bohr finds (M=N):: 
v=2:18x 10°N cm./sec. 
Now from this value of v, and v=2-47 x 10° (M—1)’, 
we can calculate x from xmv?=2hv, which must be a 
constant, because both v? and v depend on (M—1)’. 
As mv?/2 is energy to be, at least in part, radiated 
away periodically, on the right side of the equation, 
not only the number of times energy is radiated away 
per second (v), but also the total time of radiation (t) 
and the mean energy radiated away per period (E) 
must occur, so that xmv?=2tvE, and tE is a con- 
stant (which may mean only that the time during 
which radiation is emitted is inversely proportional, for 
a given frequency, to the quantity of energy that is 
radiated away during each period), Hence 
x =2hv/mv? =2.6-62 x 10-27.2-47 x 1015(M — 1)?/ 
0:88 x 10-?7,2:237 x 101°(M — 1)?=0-748, or 3/4, 
as assumed by Moseley. 
From mv?/a=e?(M—1)/a2 we  can_ calculate 
mav = e?,(M — 1) /v= 4-78? x 10~7°(M — 1) /2-23 x 108(M — 1) 
= 1-03 x 10-27, while h/27=6-62 x 10-77 /27= 1:05 x 1077", 
so that mav=h/2z, as assumed by Bohr, and 
a=5-12 x 10-°(M—1)-? cm. 
All this is in agreement with Bohr’s theory. 
As may be seen from a previous letter (NATURE, 
March 5, 1914, p. 7), some properties of the elements 
depend not on the atomic but on the “periodic” 
number P=8r+6 (r is the number of horizontal rows 
preceding that of the element period of rare-earth 
elements not counted, and p the maximum or posi- 
tive valency). Now the sum of these electrons of 
valency may be easily seen to be for all regular (non- 
elementar) inorganic molecules an integer multiplum 
of eight. Hence the same holds for the sum of all 
P electrons in these molecules (ions and rare-gases- 
atoms included). Affinity is then the tendency to 
build up systems of 8n P-electrons, and, of course, if 
such a molecule breaks up into atoms with each 
similar systems of 8n P-electrons, such ions must be 
formed as known from electrolysis. The great facility 
with which melecules like H,O, NH,, HCl, though 
neutral, are added to such systems, may be due to 
each of them, containing 8 P-electrons. According to 
Bohr, rings of electrons, whether belonging to one or 
to more atoms, may unite if the number of electrons 
in both is equal, so that rings of 2, 4, and ultimately 
8 will be the most probable (16 only if the charge is 
very great). 
Of course, the objections to the 
atom hold for such systems also. Indeed, the 
structure of the periodic system as a_ whole, 
and the curious relation between the number of the 
non-periodic (Q) elements, H, He, Co, Ni, Rh, Pd, 
and that of the horizontal rows in the periodic system : 
2/1, 2/2, 2/3, 4/3, 4/4, 4/5, 6/5, 6/6, 6/7, suggests 
systems of n equal non-coplanar rings of 8 electrons 
surrounding one or more (even n), positive nuclei, 
with m or n+1 electrons in or near the axis, and 
additional rings of electrons of valency, rather than a 
Saturnian atom. But, generally speaking, Bohr’s 
theory is not in disagreement with the atomic number 
hypothesis. A. VAN DEN BROEK. 
Gorsel (Holland), April 15. 
‘* Saturnian ”’ 
Means of Collecting Eelworms. 
Tue rhubarb, when cultivated as a field crop, is 
subject to a wasting disease, which, attacking the root- 
stock and causing it to decay, occasions considerable 
loss to the grower. The diseased tissue, when 
NO. 2323, von. @3i 
examined, is frequently found to be infested with the 
stem eelworm, Tylenchus devastatrix, Kuhn, and, in 
districts where this disease is prevalent, a supply of 
Tylenchus material is at hand which, since the rhubarb 
is a perennial plant, is available not only in summer 
but during winter also. 
When pieces of decaying rhubarb tissue are enclosed 
in a corked tube, any Tylenchus worms that are pre- 
sent migrate to the surface and, provided they have not 
been corked up too long, will, if placed in water, 
remain alive for weeks. Material can be obtained in 
quantity, and with very little delay, by placing pieces 
of rhubarb in a strainer covered with fine gauze, 
and suspended in a vessel of water. The eel- 
worms, forsaking their feeding-ground, wriggle 
through the muslin and accumulate in a writhing mass 
on the floor of the vessel. This water method, it may be 
added, is also useful in examining the eelworm fauna 
of soil samples, and pro- ; 
vides a simple means of 
ascertaining roughly 
what forms are present. 
When thus collected 
from rhubarb, the eel- 
worms are usually 
mixed with sediment, 
but wins defect - cam be %G..07 
remedied by placing the Ring 
material, while still un- 
sorted, in a _ porous 
vessel, such as a candle- 
Cotton-woor 
filter, which, when 
placed in water, allows emt 
only living eelworms to 
pass through. A_ better method of cleansing 
the material, however, is obtained by taking advan- 
tage of the habit that eelworms have of climbing up 
capillary films when these are present. For this pur- 
pose, silk threads are employed, to each of which is 
suspended a blob of cotton-wool, the cotton-wool serv- 
ing as a receptacle for holding the crude material 
obtained from the rhubarb. The upper ends of the 
threads are attached to a glass ring which is supported 
upon the sloping sides of a funnel-shaped vessel con- 
taining water—this shape being chosen in order that 
the blobs may hang clear. 
As the threads become saturated, the eelworms, 
leaving all impurities behind in the cotton-wool, ascend 
amongst the silken strands, and, passing over the 
brim into the water, congregate on the floor of the 
vessel—a feat on their part which, besides providing 
the student with clean material, raises the question 
whether, in respect of their acrobatic accomplishments, 
eelworms vary to any appreciable extent; and, if so, 
whether the rough method here described can be ex- 
tended so as to provide a means of sorting out one 
species from another, when two or more species are 
present in the material employed. 
V. LeEsour. 
a. He Tavier 
The University, Leeds. 
THE PROHIBITION OF EXPERIMENTS ON 
DOGS. 
ate Dogs’ Protection Bill for the second 
reading of which 122 members of Parliament 
were induced to vote the other day is one of those 
measures which are born of ignorance and fostered 
on misrepresentation. All our knowledge of the 
functions of the body is fundamentally based on 
experiments which have been made upon dogs. 
The action of the heart and its nerves; the 
