January 23, 1908] 



NA TURE 



271 



the paper already quoted, there should, of course, be ether 

 pulses in the X-ray stream, and the 7 stream also for that 

 matter, and it may possibly be these which have been the 

 subject of experiment by' Marx, and which show Mr. 

 Barkla's polarisation effects. But I think it is certain that 

 at least the y rays are material, and those X-rays which 

 give rise to a secondary kathode radiation of a speed due 

 to a few thousand volts. W. H. Bragg. 



The University of Adelaide, South Australia, 

 December 12, 1907. 



Drifted Ice-crystals. 



The accompanying photographs, showing the incipient 

 freezing of the sea during severe frost on January 4 at 



Littlehampton, mav be of interest to readers of N.^ture. 

 Thev were taken about high water, at 11 a.m. A high 



Fig. 2.— Layer of drifted Ice-crystals. 



N.E. wind and the flowing tide had drifted ice-crystals 

 formed on the surface of the sea into the slack water in 



NO. 1995, VOL. ']']\ 



the angle between the east side of the small pier and the 

 shore, until they were collected in a viscous layer covering 

 the whole angle. The layer seemed to be more than an 

 inch thick. 



The photographs show the border of ice-crystals thrown 

 up on the beach, with a vertical front towards the sea 

 about 18 inches high. 



The effect disappeared rapidly when the tide began to 

 fall. The timbers of the pier were thickly coated with 

 ice at high-water mark, and as far above as the splashing 

 reached, but remained perfectly clear below this line. 



\Y.\LTER Le.-vf. 



The Interpretation of Mendelian Phenomena. 

 Dr. G. Archdall Reid has recently suggested (i) that 

 Mendelian phenomena occur only under artificial condi- 

 tions, and (2) that they are to be explained in terms, not 

 of segregation, but of "latency" and "patency." As 

 regards the latter contention, it appears to me that it 

 would be justified if, in the case of e.\periments conducted 

 under stringent conditions, dominant characteristics were, 

 even occasionally, to appear in recessive generations or 

 ■nice versd ; but if this is not the case it seems an abuse 

 of language to describe a thing as " latent " which never 

 gives any manifestation of its existence. Further, Dr. 

 Reid's theory does not explain — as the Mendelian theory 

 does — why these characteristics not only appear and dis- 

 appear, but play this game of hide-and-seek in accordance 

 with strict numerical rules. 



.\s to the other point, that Mendelian phenomena are 

 confined to cultivated varieties, it is extremely difficult to 

 prove or disprove, because to ascertain the phenomena you 

 must experiment, and to experiment is to place under 

 artificial conditions. But the well-ascertained facts of 

 conjugation and cell-mitosis, which Mr. R. H. Lock re- 

 gards as affording considerable support to the doctrine of 

 gametic purity, are certainly not confined to cultivated 

 varieties. That all inheritance may be particulate was 

 long ago suspected by Galton, who speaks of skin colour 

 as possibly " a fine mosaic too minute for its elements 

 to be distinguished in a general view " (" Natural Inherit- 

 ance," p. 12). 



May I suggest one line of inquiry that may possibly 

 prove fruitful in competent hands? Is there any connec- 

 tion between the variability of a plant or animal and the 

 number or size of its chromosomes? Man, for example, 

 has a large number of chromosomes, and is extremely 

 variable. The correspondence would 

 no doubt be far from exact if we sup- 

 pose with Mr. Lock that the biological 

 units are not the chromosomes them- 

 selves, but the chromomeres or some 

 even minuter subdivisions. But it 

 might be assumed, at any rate as a 

 first approximation, that the ultimate 

 units were roughly proportional to the 

 number and size of the chromosomes, 

 J f ■ j and in that case species possessing 

 I 1 1 * p ml many and large chromosomes would 

 be likely to have a larger stock of the 

 raw material of variation than their 

 fellows. H. H. O'Farrell. 



East India United Service Club, 

 St. James's Square, S.W., 

 December 30, 1907. 



Musical Sands. 



In reply to Prof. Poynting's letter 

 (Nature, January 16), may I say that 

 the article which appeared in Nature 

 (.A-ugust 6, 1901) was only intended to 

 supplement my paper of 1888, by re- 

 cording the results of further investi- 

 gations up to date, and to show that 

 I claimed, both by analytical and 

 synthetical methods, to have proved the 

 theory previously dealt with in detail ? 

 In that paper (1888) I rejected the conception that the 

 notes emitted from musical sands were due to the vibra- 



