372 
of Sycons. Occasionally they were obtained in this 
way in fair quantity. It was therefore thought prob- 
able that a more careful examination of a number of 
these sponges would be interesting in determining 
whether this habitat is a usual one. Accordingly 
twenty specimens of Sycon coronatum, varying in 
length from about 2 to 4 cm., were examined. The 
contents of the gastral cavities of these specimens 
were squeezed on to a slide and a careful search for 
Amoeba made. 
Of the twenty specimens thus examined one or 
more Amcebz were found in all except three. Usually 
about three or four specimens were obtained from 
each sponge; only one Amoeba, however, was found 
in a few of the squeezings, but. from one sponge 
nineteen of these animals were counted, and doubtless 
not all those present were seen. It is therefore 
evident that these sponges are a common habitat of 
marine Amoebee, whence these lowly animals may be 
obtained fairly easily. 
There is no likelihood that this habitat is an exclu- 
sive one; doubtless Amcebze occur in a great many 
other situations in the sea, from which, however, they 
can only be obtained with some difficulty, 
The Amoebz obtained from the sponges were rather 
small, Specimens when measured in one common 
phase were found to be about 80 » long and 40 b 
broad, being, however, in this phase almost uniform 
in breadth, and having only slightly rounded ends, 
but when creeping such specimens stretch out to a 
length of more than 90 #. The animals move quickly, 
progressing often in a straight line and flowing with 
a motion somewhat like that of planarians; at other 
times thick, blunt, and—at first—hyaline pseudopodia 
may be extruded from one or more parts of the body. 
So far as has been observed, the animals appear to 
have a definite posterior end. The protoplasm is 
highly and coarsely granular, except at the periphery, 
and in some specimens ingested diatoms and other 
inclusions were to be seen. The contractile vacuole 
has not been made out definitely, but a stainable 
vesicle of constant size visible through a high power 
of a microscope in the anterior region of the living 
animal appears undoubtedly to be the nucleus. The 
absence of an easily visible nucleus and nucleolus 
males it easy to distinguish the Amcebe from the 
more or less amceboid forms of some sponge cells, 
which, moreover, are mostly spherical, and do not 
show anything like the active movement of the 
Amcebee. 
In their general characters these Amoeba resemble 
the species described by Gruber (Zeits. fiir Wiss. Zool., 
vol. xli., 1885, Leipzig, ‘Studien tiber Amében,” 
p- 219) as Amoeba crystalligera, but further investiga- 
tions are necessary to establish their identity with 
that species. J. H. Orroy. 
The Laboratcry, Plymouth. 
A Remarkable Meteor on November 24. 
Last night, November 24, at 8.47 p.m., a very 
remarkable meteor was seen in the northern sky. 
It moved slowly in an east to west direction, describ- 
ing a straight path of about 10° in length, which 
made a small angle (of some 20°) with the horizon, 
the eastern end being the lower, and remained visible 
for four or five seconds. 
It presented a comet-like appearance, having a 
bright nucleus surrounded by a less intensely luminous 
envelope, which streamed out behind, forming a kind 
of double tail. Conspicuous blue (or green) flares 
were visible in the “tail,” but the appearance lasted 
such a short time that I am unable to state exactly 
how they were distributed. It vanished as suddenly 
and as silently as it had flashed out. 
NO. 2300, VOL. 92] 
NATURE 
[ NOVEMBER 27, 1913 
The northern sky being overcast at the time, it was, 
of course, impossible to lay down its track relatively _ 
to the stars, but its position Was referred to some — 
tree-tops, which were silhouetted against the sky, and — 
from observations made next morning I am able to 
state that the middle point of the apparent track was — 
situated at an altitude of about 17° above the horizon, — 
and at about 7° or 8° east of the north point. 
Although seen through clouds which were sufficient — 
to obscure all stars in its neighbourhood, including — 
the conspicuous constellation of Ursa Major, the meteor — 
appeared far more luminous than the planet Venus 
even at its brightest. In fact, with one exception, it 
was the brightest meteor I have ever seen. The one — 
exception was the splendid daylight meteor of — 
February 8, 1894, which appeared in full sunshine — 
within a few minutes of noon, but was still bright — 
enough to attract the attention of thousands of people 
at various places over an extended tract of country, 
from London to Whitby, and from Chelmsford, in 
Essex, to Ballinasloe, in the west of Ireland. ‘ 
Artuur A. Rampaur. 
Radcliffe Observatory, Oxford, November 25. 
Darwinism 100 Years Ago. 
In reference to Dr. Gadow’s interesting quotation — 
from Tiedemann (Nature, November 13), may I 
remind your readers that the principle of sexual 
selection was clearly enunciated by Erasmus Darwin — 
in his *‘ Zoonomia,”’ first published in 1794? I quote 
from an edition of 1800. ‘‘A great want of one part 
of the animal world has consisted in the desire of 
the exclusive possession of the females; and these — 
have acquired weapons to combat each other for this — 
purpose. . . . So the horns of the stag are sharp to 
offend his adversary, but are branched for the pur-— 
pose of parrying or receiving the thrusts of horns 
similar to his own, and have therefore been formed 
for the purpose of combating other stags for the 
exclusive possession of the females; who are observed, 
like the ladies in the times of chivalry, to attend — 
the car of the victor. ... The final cause of this 
contest amongst the males seems to be that the 
strongest and. most active animal should propagate — 
the species, which should thence become improved.” — 
ARTHUR Denby. 
University of London, King’s College, 
November 19. 
Intra-atomic Charge. 
In a previous letter to NATURE (July 20, 1911, p. 78) 
the hypothesis was proposed that the atomic weight — 
being equal to about twice the intra-atomic charge 
“to each possible intra-atomic charge corresponds a 
possible element,”’ or that (Phys. Zeitschr., xiv., 1912, 
p- 39), “if all elements be arranged in order of in 
creasing atomic weights, the number of each element 
in that series must be equal to its intra-~atomic 
charge.” il 
Charges being known only very roughly (probably 
correct to 20 per cent.), and the number of the last” 
element Ur in the series not being equal even approx 
mately to half its atomic weight, either the number of 
elements in Mendeléeff’s system is not correct (tha 
was supposed to be the case in the first letter), or 
the intra-atomic charge for the elements at the end 
of the series is much smaller than that deduced from 
experiment (about too for Au). 
Now, according to Rutherford, the ratio of the 
scattering of « particles per atom divided by the 
square of the charge must be constant. Geiger and — 
Marsden (Phil. Mag., xxv., pp. 617 and 618, notes” 
