November, 1913. 



KNOWLEDGE. 



435 



PHYSICS. 



By Alfred C. Egerton, B.Sc. 



A SENSITIVE PRESSURE GAUGE. — M. Gueritot 

 publishes in the Comptes Rendus for June, 1913, an account 

 of a sensitive manoscope which employs thermo-electric 

 junctions to detect very small displacements of air. Two 

 vessels are connected by a tube which is bent in the middle 

 upwards ; the tube is heated at the point of the bend 

 electrically, and the heated air remains in the neighbourhood 

 of the bend. On each side of the heated portion of this tube 

 are inserted two junctions of dissimilar metals connected to a 

 galvanometer. Any displacement of the heated air causes a 

 difference of temperature between the two thermal junctions, 

 and consequently an electromotive force is set up which drives 

 a current through a galvanometer. Very small displacements 

 of the heated air can be measured ; in fact, variation of 

 atmospheric pressure by one millionth of a millimetre of 

 mercury can be detected. 



NEON AND X 3 . — Among the most interesting announce- 

 ments at the Birmingham meeting of the British Association 

 may be mentioned the experiments of F. W. Aston on the 

 separation of neon by diffusion into two constituents possessing 

 atomic weights very nearly the same, confirming in a remark- 

 able way the positive-ray experiments of Sir J. J. Thomson, 

 which showed that neon should contain two substances of 

 very nearly the same atomic weight. The other announcement 

 was by Sir J. J. Thomson about the supposed new gas, X a . 

 The atoms of a gas of atomic weight 3 had been identified 

 by his positive-ray method. The properties of this gas have 

 been recently studied by Sir J. J. Thomson, and he was able to 

 announce that it behaved as a gas with a molecule consisting 

 of three hydrogen atoms. Thus hydrogen, as well as oxygen, 

 can give rise, under the action of electric discharge, to a 

 molecule consisting of three atoms. The molecule of active 

 nitrogen, discovered by Strutt, on the other hand, is supposed 

 to consist of single atoms. 



Section A of the British Association at Birmingham showed 

 great activity, amongst the most interesting of the discussions 

 being that on " Radiation." 



ZOOLOGY. 



By Professor J. Arthur Thomson, M.A., LL.D. 



POISON OF AMPHIBIAN SKIN.— It is well known that 

 the defenceless Amphibians — toads, frogs, newts, salamanders, 

 and the like — are protected by a poisonous secretion formed 

 by skin glands. The phrynin of the toad has been often 

 experimented with, and is a powerful poison. Madame 

 Phisalix has recently found that injections of a modification 

 of Amphibian poison will immunise an animal, e.g., rabbit or 

 guinea-pig, against a strong dose of the same poison. This is 

 what might have been expected from analogous cases. But 

 the further point is of much interest— that animals immunised 

 against Amphibian poison are also immunised against the 

 poison of the viper. 



BEHAVIOUR OF FAIRY SHRIMPS.— Professor A. S. 

 Pearse, of the University of Wisconsin, has made an interest- 

 ing study of the behaviour of Eubranchipus dadayi, one of 

 the fairy shrimps. Its movements are exceedingly easy 

 and graceful. The body glides through the water slowly 

 but steadily at the rate of about a foot in ten seconds, with 

 the ventral surface usually uppermost or towards the light. 

 There is considerable dimorphism between the sexes and a 

 difference in colour that is of considerable interest. The 

 males have a delicate, translucent, almost transparent, creamy 

 colour, with reddish tail-pieces, while the females are reddish 

 throughout. The transparency of the males enables them 

 to wander about with comparatively little danger of being 

 seen, and they are thus able to seek out and fertilise the 

 females. On the other hand the coloration of the females 



makes them inconspicuous as they rest quietly in holes at 

 the bottom of the pool, or await a mate at the surface in the 

 shadow of some floating stick or other shelter. Professor 

 Pearse's point is that "the coloration of each sex is 

 apparently adjusted to its behaviour in such a way that it is 

 well protected." The males have a strong sexual appetite, 

 but as soon as a female has been provided with sperm she 

 resists the advances of males, goes to the bottom of the pond 

 in which she lives, and remains quiescent so that the eggs 

 may descend into the ventral part of her ovisac, undergo 

 fertilisation, and develop. 



RACES OF SARDINE.— Louis Fage has made a study 

 of the growth of the Sardine or Pilchard (Clupea pilchardus), 

 using the method, now so much employed, of reading the age 

 from the scales and otoliths. As in other cases, the concentric 

 striated zones seen on a scale are interrupted by several 

 clear non-striated zones, the latter indicating periods of rest 

 ("winter rings"). As Hjort has said, "the growth of the 

 scales is so closely bound up with that of the individual that 

 it is possible by simple measurements of the zones of growth 

 on the scale to retrace with real precision the history of the 

 growth of the fish." The results of his measurements lead 

 Fage to conclude that there are two distinct "biological 

 races " — the Mediterranean and the oceanic Sardine. The 

 former grows more slowly, and lags more and more behind 

 as it grows older. He proposes to study the structural 

 differences associated with this different rate of growth. 



SIGNALLING AMONG TERMITES.— Professor E. 

 Bugnion, of Lausanne (MT. Schweiz. Entomolog. Gesell- 

 schaft, XIII, 1913, page 125) communicates some very 

 interesting observations on signalling among Termites. The 

 phenomenon has been previously studied by Konig, Smeath- 

 man, Haviland, Sjbstedt, and Escherich, but Bugnion has gone 

 further. Helped by H. von Buttel-Reepen, he found that the 

 noise is produced by the soldiers, who knock on dry leaves or 

 the like with their mandibles, or with the basal piece of the 

 labium, which is exaggerated and hard. A cobra-like hissing, 

 as it seemed at first, was traced to a colony of Tertnes 

 obscuriceps which had formed its galleries on the big fallen 

 leaves of the Bread Tree (Artocarpus). From a colony in 

 Bugnion's office-desk answers used to be got to outside taps. 

 In another experiment a piece of termitary was placed on a 

 big plate and covered with stiff paper ; the soldiers collected 

 on the under surface of the paper and answered back to every 

 vibration. The noise differs in different species, but is always 

 due to minute blows on a resonating surface. The result 

 may be a rustling, or a rattling, or a crackling, or otherwise. 

 In the Indian Tertnes estherae Desneux, which turns out to be 

 the same as KSnig's Hodotertnes convulsionarius, the noise 

 made by the large and aggressive workers when they are dis- 

 turbed is like the crackling of withered leaves trodden underfoot. 

 There is evidence that the noises or the associated vibrations 

 serve to warn the workers or to reassure and encourage them. 

 There seems little doubt that they are of the nature of signals. 

 That sounds or vibrations are really perceived is made clear by 

 what was seen in the field, by the responses given by the 

 tenants of Bugnion's desk to taps from without, and by the 

 anatomical demonstration of a well-innervated sensory organ, 

 which is probably particularly sensitive to the vibrations of a 

 material like the framework of a leaf or branch, the wooden 

 partitions of the termitary, the dry walls of the fungus-growing 

 labyrinths, and so on. It is too soon to ask how much is 

 auditory and how much finely tactile. The audible signalling 

 is to be distinguished from another kind of signalling — a 

 soundless signalling — which seems to be common among 

 Termites. It is curiously like and unlike military saluting ; 

 for it seems that the soldiers salute the workers. So far as 

 we know, both soldiers and workers are sexually immature 

 individuals of both sexes. But this requires looking into. In 

 the soundless signalling the insect stands firmly on its legs, 

 with the head raised and the body slightly oblique, and shakes 

 itself for an instant with a convulsive shiver. This seems to 

 mean something to the passing worker. We cannot get 

 psychologically near enough to say more. 



