APRIL 4, 1907 | 
NATURE 
535 
and states that frogs attack carp by “ sticking fast” to 
their heads. Possibly naturalists, unknown to me, may have 
already thrown light on the origin of a tale which hitherto 
I have regarded as a fisherman’s story of the conventional 
type. 
‘On March 29 my son directed my attention to a large 
golden carp (C. auratus) lying in shallow water near the 
edge of a pond in my garden with a frog or toad apparently 
resting on its head. The fish appeared to be very sluggish, 
and made no attempt to escape from a landing-net with 
which it was easily brought to shore. On examination it 
was found that the head of the fish was held tightly by 
a medium-sized common toad (Bufo vulgaris), which had 
‘obtained a very firm grasp by inserting its fore-limbs as 
far as the second, or elbow, joint into the sockets of the 
eyes of the unfortunate fish. The ghoulish-looking toad 
lay on the top of the fish’s head facing its tail, and with 
its hind legs hanging in front of the fish’s mouth. At 
first the appearance of the eyes of the fish led me to think 
they had been ruptured, but closer examination showed 
they were merely displaced and turned partially round 
owing to the pressure exerted by the intrusion of the toad’s 
limbs between the eyes and their sockets. 
On carefully withdrawing the toad’s fore-limbs, which 
were inserted to the extent of about 1 inch within the eye- 
sockets, the eyes returned to their normal position appar- 
ently uninjured, but during their displacement the fish must 
have been quite blind. No effort of the fish could have rid 
itself of the toad after it had once obtained the remark- 
ably firm grasp which has been described, and it appears 
very probable that the fish would have died in a short 
time. How the toad in the first instance obtained a hold 
in the sockets of the fish’s eyes appears very puzzling, but 
a probable reason for its attempt to obtain a grasp, and 
for it holding on when a grasp was obtained, may perhaps 
be found in the unreasoning instinct which toads appear to 
possess at spawning time of grasping something firmly 
with their fore-limbs. A few years ago in the same pond 
referred to above I found a toad embracing a water-logged 
puff-ball so firmly that it required considerable force to 
release the fungus from the amphibian’s grasp. 
Aprian J. Brown. 
Birmingham University, April 2. 
The Atomic Weight of Nickel. 
In a recent number of Nature (February 14, p. 367) 
Dr. Barkla gaye reasons, based on experiments in con- 
nection with secondary R6ntgen radiation, for assigning 
to nickel a new atomic weight. Dr. Barkla studies the 
penetrating power of secondary Roéntgen radiation, shows 
that it depends on the atomic weight of the element, and 
from the values found for nickel, in comparison with those 
found for copper and iron, he argues that nickel appears 
to have the atomic weight of 61-3 instead of the usually 
accepted value of 58-7. 
Prof. McClelland (Trans. Roy. Dub. Soc., vol. ix., 
part i., 1905) showed that the intensity of secondary 
B radiation from different elements for the same exciting 
primary 6 rays depended on the atomic weight, and that 
a small difference in atomic weight could be detected in 
this way. According to Dr. Barkla, nickel has an atomic 
weight somewhat greater than cobalt, instead of the value, 
slightly less, given by chemists. If this were so, the 
intensity of the secondary B radiation from nickel should 
exceed that from cobalt. 
_ I have recently repeated the observations of Prof. 
McClelland, using a very sensitive apparatus. Cobalt and 
nickel gave practically the same secondary radiation; if 
there is any difference, that given by cobalt is slightly the 
greater. The values found for these elements, compared 
with those obtained for copper and iron, correspond with 
their relative positions in the table of atomic weights. 
These results obtained with secondary 8 radiation do not, 
therefore, point the conclusion suggested by Dr. Barkla, 
and are in good agreement with the chemical determin- 
ation of the atomic weight of nickel. 
I. E. Hackett. 
University College, Dublin. 
NO. 1953 VOL. 75] 
Light Sense-Organs in Xerophilous Stems. 
In view of the recent work of Haberlandt on the light 
sense-organs of leaves, it may be of interest to record 
the discovery of similar organs in xerophilous stems. 
Certain of the epidermal cells of the young stems of the 
Ephedreze have on their external wall conical structures 
of the nature of papilla, the core of the papilla being 
mucilaginous. This structure acts as a collecting lens 
focussing the incident rays of light, and a definite area 
of the cytoplasm of the back wall of the cell is thereby 
Fig. 
illuminated. 1, which is a photomicrograph taken 
aa 2 
Fic. 1.—Zfphedra Altissima showing Light Spots. 
in diffuse light of a mounted preparation of epidermis, 
shows the appearance of these light spots as seen under 
1/6 objective. 
Of any object held in the path of the incident rays an 
image is formed by each of these light sense-organs. 
Fig. 2 is a similar preparation to Fig. 1, but shows in 
each light spot the image of a hand held at a distance of 
about 2 feet in front of the microscope. 
In the xerophilous Ephedree, where the assimilatory 
work is performed by the stems, and in correlation with 
Fic. 2.—Ephedra Altissima shcwing image of hand in each Light Spot- 
which the histological character of the cortex is markedly 
similar to that found in the mesophyll of a leaf, the 
existence of such structures as these light sense-organs so 
characteristic of leaves is not by any means unexpected. 
An examination of other stems is in progress. 
R. J. D. Gravam. 
Botanical Department, University, St. Andrews, 
March 26. ; ; 
