KNn\\Li;i)ni:. 



■Makj m. I'M. 



aflcixlow occurriiiK in air, oxyKcii :iii(l other KascR iiiulfr 

 low pressure after the passage of an electric clischarKe. lie 

 had fouMil that the yelli>\v kIdw was due to the cotMbinatinn 

 of nitric oxide and o^oiic after the passaKe of the discharge 

 which formed these substances from the air passed through. 

 Hut the explanation was not (jnitc satisfactory, because it was 

 found that o/one from a Siemens' o/onisiiiK apparatus was 

 not made capable of ^ivinn the ^;low by mere rarefaction in 

 presence of nitric oxide. Professor Strult finds, however, 

 that the cause of this is the low concentration of o/one 

 produced by such methods; for on condensing out the ozone 

 as a blue explosive li(|uid and then lettinj; it vaporise into a 

 vacuum, and trealitiK it with a small quantity of nitric oxide, 

 the kIow is at once produced. He thus shows that the 

 discharge in r.irefied air produces a very considerable 

 percentage of o/one. The intermittent discharge passed 

 through air at ordinary pressure and especially at slightly 

 reduced pressure gives a yellow tlanie with a sharp apex 

 considerably above the curved path of the electric 

 current through the air. This flame is the glow produced 

 by the combination of nitric oxide and ozone. Oxygen 

 itself gives a glow of a pale whitish aspect. It has been 

 long a question whether this is due to impurity or not. 

 Professor Strutt was able to demonstrate that the glow is due 

 to water vapmu- as an impurity in very small ciuaiitity. If a 

 wire connected to a Leyden jar be coiled romid a glass bulb 

 containing rarefied pure oxygen, the afterglow can be produced 

 by the clectrodeless ring discharge ; but if a fine tube connected 

 to the bulb be immersed in liquid air, the water vapour is 

 condensed out and the afterglow is extinguished. The 

 electrodeless ring discharge has been recently investigated in 

 the Cavendish Laboratory at Cambridge. It has been found 

 to be useful in distinguishing the presence of gases in small 

 (piantities as impurities in another gas, the masking etTcct of 

 one spectrum on another being less apparent in the case of 

 the electrodeless discharge. Various spectra are obtained 

 under different pressures, and different intensities of discharge, 

 these being peculiarly evident in the case of argon, which 

 gives either a red or blue glow under the different 

 circumstances. (See Donaldson. Phil. Mafi.. October. I'Ul.) 



ZOOLOGY. 



By Professok J. Arthur Thomson, M..A. 



WHALES' HAIRS. — .Although hairs are reduced to a 

 ininimum in Cetaceans, there is probably no species entirely 

 without them. Dr. .Arnold Japha has recently studied five 

 baleen whales and six toothed whales, and has found hairs 

 about the lips of them all. Apart from their great reduction 

 in number, they show distinct signs of retrogression. The 

 hair-muscles and glands have gone, the hair-shaft is greatly 

 reduced, the root-sheath is simpler than usual, and there is no 

 hair casting. On the other hand, there is very interesting 

 specialisation, notably in the rich supply of nerve-fibres and 

 in the way these end in the hair-follicle. There may be four- 

 hundred nerve-fibres to one hair, so that if there are twenty-five 

 hairs on the chin there are ten thousand nerve-fibres on a 

 small area. In the toothless Cetaceans at least it seems 

 highly probable that these sensitive hairs play a role of some 

 importance in food-getting. 



KICPKOIHCTION OF BROWN RATS.— The economic 

 and medical importance of the brown rat makes it particularly 

 desirable that we should know as much about it as possible. 

 Newton .Miller has furnished some precise data as to the 

 details of reproduction, — based on the study of rats in 

 captivity. The creature breeds all the year round. The young 

 are carried from twenty-three and a half to twenty-five and 

 a half days before birth. The number in a litter varies from 

 six to nineteen, with an average between ten and eleven. Five 

 or six litters may be actually re,ired by a single pair in the 

 course of a >'ear. If the young are destro\ed or renio\ed at 

 birth, there m.iy probably be a litter every month ; in one case 

 seven litters were produced in seven months by one female. 



There is very little in the way of courtship. Smell seems 

 important in sex recognition. Males fight persistently with 



one another and the conquered afterwards try to elude the 

 victors. The females may, and usually do. resist the 

 males for a little while, but they soon give up the contest. 

 .'\fler the fighting period, males will often permit themselves 

 to be severely punished by the fem.des without injuring them. 

 Brown rats in captivity eat almost fifty per cent, of their young 

 at birth; and mostly, if not always, the females are the 

 culprits. They do this even when apparently undisturbed, 

 and even when they are getting meat in their diet. The 

 expl.'ination remains obscure. Brown rats .-ire not full grown 

 before eighteen months, but sexual maturity is reached by 

 both sexes not later than the end of the fourth month. 



RESULTS OF IMPRISONMENT IN DARKNESS.— 

 J. Ogneff kept gold-fishes in a roomy tank and with plenty of 

 food (earthworms and Cliiroiioiiius larvae), but in absolute 

 darkness. He kept it up for over three years, and then 

 observed the modifications that had occurred in the fish. The 

 colour first became black, but after the second year it became 

 golden again, and the reason for this is interesting. In the 

 first instance the dark pigment-cells spread out, and covered 

 up the subjacent layer of crystals which gives the gold-fish its 

 golden sheen. In the second instance the phagocytes devoured 

 the dark pigment-cells and thus re-exposed the golden layer. 

 The changes in the eye were even more interesting. The 

 structure of the pigment- epithelium of the eye was completely 

 altered, and there was a complete disappearance of the rods 

 and cones, and of some other characteristic layers of the retina. 

 Profound atrophy of the eye occurred. The fish became 

 totally blind. OgnefTs experiment suggests that an individual 

 fish imprisoned in a perfectly dark cave would become blind. 

 But it does not throw any direct light on the origin of a blind 

 race of fishes in caves. 



DEFENCES OF BIVALVES.— Everyone is familiar with 

 the elaborate outgrowths from the surface of some Lamelli" 

 branch shells, which seem like a waste of shell-making 

 material and energy. Mr. Cyril Crossland propounds a 

 theory of their significance, — that they are often protective. 

 In some species they are larger in the young forms and thev 

 are of value during the relatively more active period when the 

 young pearl-oyster, or Avicula, or Tridacna is crawling about 

 and seeking a suitable place for settling down on. .An enemy 

 like the shell-eating fish Balistes prefers those with weaker 

 shells. .Another enemy, the boring Gasteropod .\Iurex. kills 

 more of those with smoother shell. Thus it kills large 

 numbers of Margaritifera maiiritii which has small and 

 weak processes, but few ot Margaritifera margariti/era 

 which has large strong processes remaining well-developed 

 for at least six years. It seems that the strong processes 

 prevent the Murex from readily getting a firm hold with its 

 foot, and without this it cannot work the drill in its proboscis. 

 Mr. Crossland explains how the Murex often kills the bivalve 

 without boring. " It finds the flexible edge of the shell, then 

 by contractions of its foot breaks a piece away. The mucus 

 of the foot-glands is then poured out in quantities, and this 

 has some poisonous effect, as the animal, while still untouched, 

 ceases to respond to the stimuli which ordinarily cause a 

 smart closure of the shell." 



SENSITIVENESS OF SEA-URCHINS" PEDICEL- 

 L.ARI.AE. — In experimenting on the sensitiveness of a sea- 

 urchin {Toxopneustes varicgatus) to a shadow cast upon it 

 in the water, Dr. R. P. Cowles discovered a remarkable fact — 

 that the snapping spines or pediccllariae react quite definitely 

 even after being cut off from the body. There are two kinds, 

 big and little, which respond differently to stimulus. One of 

 each kind was placed in a large dish of sea-water, and exposed 

 to direct sunlight ; the large pedicellaria opened its jaws, and 

 the small one shut its jaws. When, however, a patch of 

 shadow was thrown upon them, the jaws of the former closed 

 while those of the latter opened. The change of the reaction 

 resulting from a change in the intensity of the light stimulus 

 was repeated many times with these two pediccllariae. The 

 experiment proves that the pediccllariae act independently of 

 the radial nerve, and confirms the view of von Uexkiill that 

 the pediccllariae have the dignity of a reflex person. 



