April i6, 1908] 



NA TURE 



559 



the subject either tedious or involved. It is, on the 

 contrary, an eminently readable and attractive 

 volume. It is divided into chapters describing the 

 Ijrcparation and reactions of the diazo-compounds, 

 their derivatives, and their constitution. In an appen- 

 di.\ a short account is given of the author's new theory 

 of their structure. This is not the place to enter 

 upon a discussion of the subject, but a strong- case is 

 made out for the new view, which should stimulate 

 fresh experimental work of an interesting character. 



J. B. C. 

 Handbuch dcr I'hysik. By Dr. A. \\"inkelmann. 

 Second edition. Fifth volume, second part : Elek- 

 trizitat und Magnetismus, II. Pp. .\iv + 97i; illus- 

 trated. (Leipzig : J. .\. Barth, 1908.) Price 

 16 marks. 

 The present portion of this encyclopeedic treatise con- 

 sists of electrodynamics and induction, by K. Waitz ; 

 absolute measurements of magnetic and electric quan- 

 tities, by A. Oberbeck ; technical applications of in- 

 duction, by Th. des Coudres ; telephony, by L. Rell- 

 >tab ; and the theory of electric phenomena, by L. 

 Graetz. Important though every one of these sections 

 is, it is doubtless to the last that the reader will turn 

 first on account of the great developments of theory 

 during the last decade ; and especially will he turn to 

 the chapters on electrons and on the electromagnetic 

 equations for bodies in motion. We have stated in 

 review-ing the previous parts that the treatise is not 

 intended for continuous reading. It is essentiallv an 

 encyclopaedia, a book of reference. But it is the 

 treatise per excellence to which reference should be 

 made by all those who w-ish to know what has been 

 done and what theories have been enunciated in the 

 domain of physics. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. 'I 



The Condensation of Helium. 

 I.N N.xTL'RE of March 12 I have found a note referring 

 to my experiments on the expansion of helium, made in 

 consequence of my determinations on the isothermals of 

 helium, at —252° C. and —259° C, which yielded nearly 

 — 5° K. for the critical temperature of helium. 



The prosecution of the experiments has shown that 

 what I observed in expanding the gas was not the evapora- 

 tion of solid helium, but solution phenomena of solid 

 hydrogen in gaseous helium. I have cominunicated to the 

 Amsterda.Ti .Academy a note on my experiments, which 

 at the moment leave the condensation of helium a yet 

 undecided question. 



Of course, I have written the details to Sir James 

 Dewar, and I hoped to do so to you to-day, but by press- 

 ing duties I cannot do it before to-night, and you will 

 probably go to press before that letter reaches you. So 

 I beg to be allowed to send you first this short notice. 

 Leyden, .April 14. H. Kamerlingh Oxnes. 



Mendelian Characters among Shorthorns. 

 Prof. Wilson is welcome to any satisfaction he can 

 obtain out of the Mendelian interpretation he gives to 

 our statistics of coat-colour in Shorthorns. .As a matter 

 of fact, some readers may consider that the same inter- 

 pretation is given with greater numerical accuracy on 

 pp. 440-4 of our original memoir (Biometrika, vol. iv.). 

 For example, we give 656 crosses of roan and wliole red 

 alone, resulting in 243 whole reds, eighty-five red and 

 whites, and four whites^. The remainder consists of 324 

 roans, Of this we say " the close approximation to the 

 Mendelian number of the roans is noteworthy, but the 

 appearance of 4(WW) is again impossible unless some of 



XO. 2007, VOL. 77] 



the reds are to be treated as heterozygous." Why does 

 Prof. Wilson reduce our total red roan crosses to 456, and 

 leave out the inconvenient four whites? Why does he give 

 only three whites crossed by white as giving three whites, 

 while we dealt with ninety-one such crosses giving eighty- 

 six whites, four roatis, and one red? Why, further, does 

 he leave out the whole of our Table L on p. 441? We - 

 followed up the white cattle pedigrees, writing to the 

 breeders about special cases, and finding in the great bulk 

 of instances the crosses and colours stated in the Herd- 

 book confirmed. If it be asserted that the colours given 

 in the Herd-book are incorrect, or, still more vitally, that 

 the confirmation of those facts given to us by reputable 

 breeders are misstatements, then the only conclusion is 

 that Mendelism cannot be discussed on the basis of the 

 Shorthorn data. That is a logical position ; it is not, 

 however, logical to use the data, and escape inconvenient 

 facts by the statement that they are due to errors or to 

 deception, or to omission to enter calves (which we found 

 on inquiry among English large breeders to be not so 

 frequent as has been asserted). 



The facts stated by us on p. 442 of our paper, which 

 cannot at present be made fully public, show that there 

 are probably latent colour determinants in white cattle 

 which can be made patent if two individuals of pure white 

 coat, but one of mixed race, be crossed. Recent experi- 

 ments seem to show that the actual amount of pigmenta- 

 tion in the coat is an inherited character in mammals ; no 

 explanation, Mendelian or other, which overlooks the 

 difference between whole and parti-coloured animals can 

 in the present state of our knowledge be considered satis- 

 factory. .As it is, the parti-coloured cattle are being bred 

 out, and the possibility of this shows that red and parti- 

 colour .are not interchangeable. This point is illustrated 

 again by the fact that in whole red crossings about 3 per 

 cent, of roans appear, but in parti-colour crossings about 

 8 per cent, of roans occur. There is at the bottom of 

 this, I believe, a physiological fact, and I am not pre- 

 pared to overlook it by saying, with Prof. Wilson, that 

 438 red by red matings gave twenty-five roans, which are 

 to be put down as due to errors and misstatements because 

 thev do not fit his view of the case. 



Within broad .lines Shorthorns do show segregation in 

 the results of the crossings ; this is really the great idea 

 embodied in the Mendelian view. It may be possible on a 

 determinantal theory to offer a reasonable account of the 

 Shorthorn data ; such a theory would certainly follow recent 

 Mendelian work in discriminating between whole and parti- 

 colour coats. On the other hand, it is a possible attitude 

 to discard the data as untrustworthy ; it is not logical, I 

 hold, to discard just as much as you please of the data 

 and no more in order to make it fit the simpler Mendelian 

 ratios. Karl Pearson. 



Biometric Laboratory, University College. 



The validity of Prof. Pearson's criticism of the view 

 that Shorthorn cattle are Mendelians turns upon the 

 accuracy of my statements (a) that in the Herd-book 

 roans are sometimes registered as reds and reds as roans ; 



(b) that many white calves are not registered at all ; and 



(c) that coloured calves are sometimes substituted for 

 white ones. Unfortunately, these statements are all true, 

 although the last one only need cause very serious regret. 

 The following may make the position clearer. 



.A short time ago a very distinguished breeder was re- 

 gretting the substitution of coloured calves and the 

 difficulty of proving cases of substitution to be such. This 

 breeder persistently uses white bulls in order to get roan 

 calves from his red cows, and, in proof that red calves 

 entered in the Herd-book as the progeny of reds and 

 whites are probably substitutions, he mentioned that in all 

 his experience he had got only one red calf from his white 

 bulls and his red cows. 



That red calf — a bull — came to Ireland, and is still alive. 

 To the great disappointment of his owner, he has bred 

 several white calves from roan cows. 



First, by being the son of a white bull and a red cow. 

 and, next, by breeding white calves from roan cows, this 

 red bull disproves the theory that Shorthorns are 

 Mendelians ; but I had the privilege of seeing him this 

 afternoon, and he is not red, he is rcr.:t. He is, however, 



