152 



KNOWLEDGE. 



April, 1913. 



great feat to have accomplished the actual making visible of 

 phenomena which have only been investigated and understood 

 by process of reasoning ; things are understood clearest when 

 they are made to appeal to the visual sense. 



Among other lectures of great interest may be mentioned 

 Professor Sir Joseph Thomson's lectures on the Constitution 

 of the Atom, which have just been terminated at the Royal 

 Institution. He expounded in these lectures simply and 

 clearly his view of the atom composed, as all now admit, 

 partly of negative electrons and partly of positively charged 

 matter. The atom possesses a central core of electrons and 

 an outer ring, and the maximum number of electrons in this 

 ring is eight. The number in the ring determine the valency 

 of the atom, and the vibrations (as of a conical pendulum) 

 determine the type of spectra emitted. It would be too much 

 to go into the subject in detail in these notes, and the same 

 also applies to the interesting account of the researches of 

 Professor Nernst, which he expounded on four evenings 

 following the 6th March, to a large audience, at University 

 College, London. 



ZOOLOGY. 



By Professor J. Arthur Thomson, M.A. 



A MOUTHLESS CARP.- -It seems strange that a fish can 

 live and thrive without a mouth. J. W. Fehlmann describes 

 this apparent simplification of life on the part of a carp four 

 years of age. Its mouth was absolutely shut and the same 

 was true of the anus. Yet there were numerous mayfly 

 larvae, crustaceans, pieces of plants and the like in the food- 

 canal. The animal must have not only breathed but fed 

 through its gill-clefts. We are not surprised to learn that the 

 carp showed no trace of fat, but to live for four years without 

 a mouth was certainly an achievement. 



MOVEMENTS OF THE SEA-HORSE.— R. Anthony and 

 L. Chevroton have studied the attitudes and movements of the 

 fascinating Hippocampus, which is at once a fish of the floor 

 of the sea (benthos) and " arboricolous " among the sea-weed. 

 It fixes itself upright with its prehensile tail, and is helped by 

 its swim-bladder to keep the vertical position. It swims 

 vertically, or obliquely, using its pectoral fins, and the dorsal 

 fin usually helps. The dorsal fin is also used to steady the 

 animal when it is fixed by its tail. In moving towards an 

 object the sea-horse bends forwards a little and mounts 

 upwards. When it descends it stops the action of its fins. 

 There are many remarkable specialisations about this attrac- 

 tive little creature. Thus there are numerous individualised 

 muscles. The head is not in a line with the backbone, but at 

 an angle of 90°— 100° to it. 



NATURAL HISTORY NOTES FROM BOLIVIA AND 

 PERU. — Mr. James Murray, who was naturalist on Sir Ernest 

 Shackleton's Antarctic Expedition, now sends some very in- 

 teresting notes from a very different part of the world — from 

 Bolivia and Peru. The rapidly-dwindling Echoja Indians have 

 great skill in wood-craft. The chief Wahshee could bring the 

 animals to him by uttering certain sounds, which did not seem 

 to be imitations. " On one occasion a deer was sighted. 

 Wahshee began a very loud and wild cry, and the deer came 

 slowly nearer and nearer, till it was only two or three yards 

 from us." " On another occasion it was a black monkey. 

 This time he used a quite different sound, a very plaintive, 

 weird kind of whimpering. The monkey began to climb down 

 the tree towards us, and came quite near before something 

 disturbed it." 



MAGGOTS IN MAN. — Mr. Murray gives a grim account 

 of one of the common scourges of the forest, the Sututu 

 (Dermatobia cyaniventris), a two- winged fly, whose larvae 

 — about an inch long — occur in the skin of men and beasts. 

 They are like Indian clubs in shape and bear rows of 

 prickles. The presence of the parasite is usually first noticed 

 on account of the sharp pain caused by the prickles as it 

 moves. The chief Wahshee already alluded to seemed to be 

 able to summon the larvae out of the skin by making a 

 curious chirping noise with his mouth, but there is need for 



sceptical criticism here. Worse than Sututu is the Screw- 

 Worm (Chrysomyia macellaria) also the larvae of a horse- 

 fly. Large numbers occur together in the skin about a 

 wound. They burrow restlessly and cause great pain. They 

 kill many mules and a few men, and are themselves singularly 

 difficult to kill. The great specific seems to be a medicament 

 called Cebadilla. 



THE SCALLOP'S EYES. — Numerous well-developed eyes 

 occur along the margin of the scallop's mantle, and it is well 

 known that the bivalve is exquisitely sensitive to differences 

 of light and shade. Victor Bauer has made a series of careful 

 observations on Pecteu jacobaeus, and finds that one great 

 use of the many eyes is to direct the animal to the illumined 

 surface areas, where there is special abundance of the phyto- 

 plankton on which it mainly feeds. The scallop does not 

 steer when it swims, it gets its bearings by means of its eyes 

 before it starts. The eyes also help it to detect the movements 

 of an approaching enemy, and the stimulus leads to a shutting 

 of the shell-valves. The skin secretion of a starfish sets the 

 scallop a-swimming, and here tactile and chemical stimuli 

 operate. But the eyes are auxiliary. 



COLOUR-SENSE IN BEES.— Very interesting experi- 

 ments by L. von Dobkiewicz throw a clear light on a much 

 discussed question and on a number of well-established but 

 discrepant facts. It seems certain that bees distinguish 

 different colours. But different colours acquire significance 

 for bees when the insects have learned that certain colours 

 are associated with certain nutritive advantages. The bees 

 are not " reflex-machines," they are not compelled by any 

 organic chromotropism to prefer certain colours to others. 

 They accumulate experience, and remember that certain 

 colours are associated with certain nutritive benefits. They 

 learn to save time by following certain colour-hints, but it is 

 not inconsistent with this that they are eager visitors of 

 flowers without any colour at all, but rich in nectar none the 

 less. 



SENSE OF DIRECTION.— Edmond Bordage made a 

 study of digger-wasps and other insects at Reunion and 

 reached some interesting conclusions. He maintains, for 

 instance, that the wasps find their home again by taking 

 particular notice beforehand of the immediate surroundings. 

 As the Peckhams noticed, there is a preliminary scouting and 

 observation of surroundings before the insect quits the 

 vicinity of the nest. Bordage is unwilling to invoke a special 

 sense of direction in such cases. 



OXYGEN-STARVATION.— Anna Drzewina and Georges 

 Bohn have made interesting experiments showing the indiffer- 

 ence of many marine animals to scarcity of oxygen. A small 

 shore-crab (Carcinus tnaenas) lived for twenty-two hours 

 in water with only a trace of oxygen, and soon recovered. 

 A pea-crab {Pinnotheres) survived for three days. A 

 small sea-anemone (Metridium dianthus) lived for four 

 days, and others {Anthea cereus) seemed to be quite normal 

 after four and a half. The little periwinkle (Littorina rudis) 

 was none the worse for four days of the oxygen-starvation and 

 a Polychaet [Phyllodoce laminosa) was living after thirty- 

 nine hours. The little starfish, Asterina gibbosa, recovered 

 itself after thirty-four hours. In most of these cases, the 

 animal was inert at the end of the experiment, but recovered 

 in the course of a few hours. 



VESTIGES OF SCALES IN SIREN.— It is well known 

 that amphibians are almost always quite naked, thus standing 

 in great contrast to the scaly reptiles. The limbless Caecilians 

 which burrow underground are exceptions, for they have 

 numerous scales embedded in the skin ; and there are some 

 other exceptions, such as Ceratophrys, which has bony plates on 

 its back. The extinct Labyrinthodonts were also armoured. In 

 studying the mud eel, Siren lacertina, Margarethe Kressmann 

 has made a very interesting discovery. There are numerous 

 papillae in the deeper, firmer layer of the underskin or dermis. 

 They occur over the whole body, and although they are hidden 

 by the more superficial layers of the skin, their structure is 

 such that they are very reasonably interpreted as dwindling 

 vestiges of the scales which ancestral amphibians possessed. 



