570 



NA TURE 



[October S, 1908 



This line of thought raises questions as to the effect of 

 the enormous mass of positive luminous vapours partici- 

 pating in the solar rotation. Will it give rise to magnetic 

 ■tfects? Perhaps not if ether is dragged with the sun; 

 .It any rate, a charged body rotating with the earth 

 seems to produce no magnetic field. If, however, there 

 are solar atmospheric currents on a large scale magnetic 

 efTects may be expected. If the sun is thus magnetised 

 it would act inductively on the earth, and the magnetism 

 of the earth might be thus accounted for. The sun's 

 north pole should be positive to account for the negative 

 polarity of the earth's geographic pole, and it is interest- 

 ing to note that such would be the case if the sun's 

 polarity is due to positively charged vapour rotating 

 with it. 



It would likewise follow that the moon is an induced 

 magnet. It might be worth while for someone to consider 

 the effects upon perturbations of earth and moon of the 

 force moments due to the non-coincidence of the polar 

 .ind magnetic axes. 



If the supposed positive charges in the chromosphere 

 arise from the projection of electrons into space, the 

 accumulation of the latter in outer regions would produce 

 with the positive atmosphere an enormous electrical double 

 layer, with a radial field which would restrain further 

 travel of the electrons and perhaps cause the tremendous 

 outbursts of luminous positively charged vapour shown 

 in prominences. Magnetic effects in these prominences 

 should be looked for. 



Very light ions (perhaps of some lighter element than 

 any we know) might be drawn from the sun by the 

 electric field, and their subsequent neutralisation by 

 electrons may give rise to coronal line radiation. These 

 encounters, always taking place in radial lines, may give 

 rise to partially polarised radiation, but it must be con- 

 fessed that it seems difficult to reconcile the effects which 

 would probably follow with the observed direction of 

 vibration in coronal light. E. Percival Lewis. 



University of California, .September 14. 



Memory in the Germ-plasm. 



It has recently been suggested that acquired characters 

 are transmitted by a kind of memory in the germ-plasm. 

 If this suggestion were adopted, would it not enable us 

 to explain the non-transmission of mutilations? 



If there be such a connection between the somatic-cells 

 and the germ-cells as this new theory presupposes, that 

 connection must be constant. We must suppose the germ- 

 cells to be a kind of registry in which all the events of 

 the somatic life are recorded. Many of the records would 

 be evanescent, just as many of the records in consciousness 

 are evanescent, but important somatic changes would (bv 

 the accumulation of impressions) produce perduring 

 records, and these would be the biological ground of the 

 transmission of those changes to the new generation. 



Now- consider what happens in mutilation. A lamb's 

 tail is shortened — what is the result in germ-meniorv? 

 Merely the record of a momentary cut. Why should this 

 be transmitted? There is already in the germ-memory 

 the record of an undiminished tail — a record produced by 

 thousands of impressions accumulated through every 

 moment of the animal's earlier life. Naturally, this record 

 will be prepotent over the record of a momentary event. 



We must remember, too, that the nerves and muscles 

 of a stump often strangely preserve for a long time what 

 may almost be called a recollection of the amputated part. 

 If the lost limb thus perpetuate itself (so to speak) in 

 consciousness, it seems prob.able, c.v hypofhesi. that it 

 similarly perpetuates itself in germ-memory. Moreover, 

 a man who has lost a leg constantlv tries (consciously or 

 '■ubronsciously) to act as though he still had it. This, 

 ngain, one may suppose, would tend to perpetuate the 

 germ-record of the lost member. 



It seems, then, that, in a case of mutilation, the record 

 in germ-memory of the momentary act of mutilation would 

 be an evanescent record, and the germ-record, as a whole, 

 would continue to be the record of an unmutilated body. 

 Does not this help us to understand the non-transmission 

 of mutilations? Hakli-yt Egerton. 



NO. 2032, VOL. 78] 



Models of Plane and Spherical V\^aves. 



It is very easy to form a mental picture of the displace- 

 ments in an isotropic elastic solid transmitting a plane 

 transverse wave. Alternate planes of constant phase are 

 sheared relatively to one another, as explained in 

 Schuster's "' Optics," § 12. If this be a correct repre- 

 sentation of the process of transmission, it should be 

 possible to apply a similar method to the alternate 

 spherical shells in the transmission of a spherical wave. 

 The shears must obviously possess symmetry about the 

 point centre of the disturbance, since the waves are trans- 

 mitted uniformly in every direction. This appears to me 

 to be impossible ; but if such shears are impossible in a 

 spherical wave it is absurd to apply them to a particular 

 ease of the spherical wave, viz. a plani^ wave. Will some 

 kind friend please explain? J. J. D. 



The following explanation may be helpful if I under- 

 stand the difficulty aright. 



Imagine a number of concentric spherical shells like 

 the layers of an onion. Imagine the inside shell rotated 

 about a diameter through a small angle, and imagine 

 this displacement taken up in succession bv the next shell, 

 the next but one, and so on. Then we have a disturbance 

 radiating outwards from the centre, but the wave motion 

 is not symmetrical about the centre. If, however, we go 

 to a long distance from the inside sphere along a per- 

 pendicular diameter we get practically plane waves. 



But these plane waves are in no way the limiting case 

 of spherical waves symmetrical about a point, for the 

 vibrations take place in a particular direction (in other 

 words, they are plane polarised). It is impossible to have 

 shears in plane waves which possess the symmetry re- 

 ferred to by your correspondent. A pack of cards can be 

 sheared parallel to its longer or shorter side or to its 

 diagonal, but it cannot be sheared at the same time 

 equally in all directions. There is no difference between 

 plane and spherical waves in this respect. Light spread- 

 ing out uniformly from a source is a very different thing 

 from these simple plane and spherical waves. It repre- 

 sents a jumble of waves sent out from a large number of 

 molecules, and these molecules are not only moving about 

 and changing their positions, but are themselves rotating. 

 The radiations they emit are probably different from the 

 motions of the spherical shells described above, but these 

 do bv wav of illustration. G. H. B. 



The Pendulation Theory. 



In Nature of .April 2, 190S, the reviewer of my " Pendu- 

 lationstheorie," Mr. R. L., directed, attention to the map 

 which shows the distribution of the ichthyosaurs, because 

 I have left out the .\frican ones. He therefore thinks it 

 difficult to commit himself to an opinion on the theory. 



Those ichthyosaurs in .Africa (not yet marked in the 

 edition of Zittel's " PaU'Eontology " I have used) are not 

 in the least an argument against my theory, but give 

 me another most striking proof of it. I had shown that 

 the ichthyosaurs had taken their origin under the pendu- 

 lation circle, and had wandered from there on the usual 

 line south-eastward to New Zealand. For they have been 

 found under the pendulation circle from Spitsbergen to 

 Sicily, all the others on a line from Europe to New 

 Zealand. 



Their having been found in .Africa only enlarges their 

 extension along the pendulation circle, and so confirms my 

 opinion that the ichthyosaurs have here taken their origin. 



.\nother instance, quite recently discovered, offers the 

 fluviatile medusa Limnocodium. Until recently it was only 

 known in aquariums; it was first found in England, and 

 described by Lankester. Its occurrence together with I'lV- 

 toria rcgia proves that its origin is in the tropical parts of 

 .America. .Some time ago Prof. Oka described a second 

 species from the upper Vang-tse-kiang. That is just the 

 same discontinuous occurrence which I have pointed out. 

 for instance, for the alligators, and which I have made use 

 of for the nendulation theory. H. Simroth. 



Leipzig, Gautzsch, -August 2:. 



