532 



NATURE 



[October 19, 191 1 



I 



THE FOURTH INTERNATIONAL 

 CONFERENCE ON GENETICS. 



^HE fourth International Conference on Genetics is the 

 latest of a series of conferences which was in- 

 augurated with the " Conference on Hybridisation " con- 

 vened in 1899 by the Royal Horticultural Society. The 

 Horticultural Society of New York undertook the organisa- 

 tion of the second conference, held in that city in 1902 ; 

 the third " Conference on Plant-breeding " took place in 

 London in 1906, again under the auspices of the Royal 

 Horticultural Society ; the fourth conference of the series, 

 and the first to receive the title of " Conference on 

 Genetics," has recently been held in Paris under the control 

 of the Societe Nationale d'Horticulture de France, which 

 is to be very heartily congratulated on the success which 

 attended all its arrangements. 



As M. Ph. de Vilmorin has pointed out, genetics, 

 though born of the studies provoked by the rediscovery of 

 Mendelism, is itself of wider scope, and includes all that 

 appertains to the physiology of heredity, the problems of 

 fluctuating variation, selection, mutation, the transmission 

 of acquired characters, cytology, &c. Most of the subjects 

 were represented among the communications brought before 

 the recent conference. There were, indeed, no papers deal- 

 ing purely with cytology, though Dr. Swingle brought for- 

 ward the tentative suggestion that the diverse types 

 encountered in certain F, families might be due to different 

 groupings within the cell of a given set of determinants ; 

 but the absence of cytological papers no more than reflects 

 the present difficulty of producing any satisfactory cyto- 

 logical " explanation " of the phenomena of heredity, and 

 we can only hope for better things in the future. Appended 

 are short notes on a few of the communications made to 

 the conference. 



Messrs. Bateson and Punnett described some results of 

 very great interest in regard to the special relations which 

 have been found to exist in certain cases between distinct 

 factors. Those who have followed recent progress in this 

 work will remember that in not a few crosses, between 

 plants differing from one another in respect of two 

 characters, the phenomenon known as " partial coupling " 

 between the factors for these characters has been ex- 

 hibited ; that is to say, the F, produces the four possible 

 types of gamete, not in the approximately equal numbers 

 which would result from a chance distribution of the 

 factors, but in proportions represented by the general 

 expression 



(n-i)AB :.iA6 : iaB : (n-i)nb, 



where n is any power of 2 and is equal to one-half the 

 total number of gametes produced. 



Other crosses, on the other hand, gave results which 

 suggested that, in certain circumstances, the same two 

 factors wer>3 repelled from one another in gametogenesis. 

 Unlike the phenomena of coupling, the repulsion appeared 

 to be complete, so that no germ-cell received both factors, 

 and consequently no germ-cell was without one of them. 



This year, however, Punnett has discovered a 1 ase in 

 which repulsion is not complete, but the gametes contain- 

 ing one or other of the two factors (but not both) are pro- 

 duced in greater numbers than the other types of gamete. 

 I hat is to say, the middle terms of the gametic series are 

 large, the end terms small — the converse to what occurs 

 in " partial coupling " — and the gametic series is repre- 

 sented by the expression 



iAB : (n- i)A6 : (n- i)aB : lab. 



In Punnett's case the gametic series was of the form 

 1:3:3:1; even in this case, where n has its lowest value, 

 only one plant having both recessive characters is to be 

 expected in every sixty-four F, plants. With higher values 

 of n, the proportion of double-recessives in F\ will be 

 smaller still, and it can scarcely be doubted that this is 

 the explanation of the cases hitherto regarded as repre- 

 senting complete repulsion ; at the same time, the isolated 

 occurrence of double-recessives in families exhibiting re- 

 pulsion is explained. 



The di-hvbrid F, may therefore produce the four types 

 of gametes in proportions ranging from 



XO. 2I90, VOL. 87] 



thiough 



I" -1) 



(«-l) : («-l) 



Bateson and Punnett point out that the conception 

 underlying the terms *' partial coupling " and " repulsion " 

 is no longer justified, and they substitute the phrase 

 " reduplication of terms " in a series of gametes. 



Profs. Baiir and Lotsy described experiments in cross- 

 ing different species of snap-dragon. Antirrhinum majus 

 (in the normal and peloric forms) was crossed reciprocally 

 with A. molle, with A. latijolium, A. sempervivum, &c 

 The characters of the hybrids and of the very numerous 

 forms obtained in F a were illustrated by means of coloured 

 drawings. The experiments showed conclusively that 

 segregation takes place in these species-crosses ; how 

 numerous are the factors to be considered may be judged 

 from the fact that, of the 500 F : plants raised, scarcely 

 any two were alike. Among these plants there appeared 

 an interesting new type resembling the flowers of the 

 yellow-rattle (Rhinanthus) in the shape of the corolla. 



Several papers dealing with cereals were presented, some 

 of them of no little importance from the economic point of 

 view. Dr. Nilsson-Ehle described experiments indicating 

 that precocity and resistance to cold depend upon combina- 

 tions of Mendelian factors. Dr. Surface described the 

 results of selection for such characters as protein-content, 

 &c. He showed that in one case of successful selection 

 for high protein-content, the plants raised after the ninth 

 generation were all the descendants of a single progenitor, 

 that is to say, selection had resulted in the isolation of a 

 pure line possessing the desired quality. This result agrees 

 with much that has been done since Johannsen first clearly 

 presented the idea of pure lines, and agrees, too, with the 

 new results which Prof. Boeuf communicated on the present 

 occasion. 



Dr. Orton described some work of the highest economic 

 importance in the raising of varieties of agricultural plants 

 resistant to the attacks of disease. Many varieties of 

 cotton, the cow-pea (Vigna), and the water-melon are 

 susceptible to the attacks of species of Fusarium ; the cow- 

 pea, in addition, is liable to the attacks of the nematode 

 Heterodora radioicola. Immune or highly resistant varie- 

 ties of all these plants have now been obtained, in the 

 case of the water-melon, however, only after crossing with 

 a non-edible but resistant wild type. 



At the session devoted to papers dealing with animals. 

 Prof. Federley described an interesting case in Pygaera of 

 the transmission of a disease through females, themselves 

 unaffected by the disease, to their male offspring, all of 

 which died of the disease. Dr. Walther, of Vienna, gave 

 an account of his investigations into the inheritance of 

 coat-colour in horses, a subject with regard to which he 

 has secured a great wealth of material. 



Finally, mention must be made of a new case of brai hy- 

 dactylv in man, described by Dr. Drinkwater. This case 

 differs from the previous one in that there is no ankylosis 

 of the short median phalange with the terminal phalange, 

 and the fingers are intermediate in length between the 

 extreme brachydactylous and the normal types. The 

 abnormality is present in about one-half of the members 

 of the affected family. 



Much as there was of interest in the proceedings of the 

 conference, not the least memorable of its features was the 

 visit which the members were privileged to pay to the 

 establishment of MM. Vilmorin, Andrieux et Cie. at 

 Verrieres-Ie-Buisson. One's only regret was that the time 

 at our disposal was all too short for even the most cursory 

 inspection of th. wonderful collection of plants which has 

 been gathered together here, and of the experiments 

 in breeding and selection which are being carried on 

 by M. Ph. de Vilmorin himself and by the firm of which 

 he is the head. It is useless to attempt in a limited space 

 to give any detailed description of Verrieres : it need only 

 be said that the whole establishment, gardens and museum 

 alike, admirably reflects the enthusiasm which M. Ph. 

 de Vilmorin. like the members of his family who have 

 preceded him, has always shown for the scientific as well 

 as the more obviously practical asperls of horticulture and 

 plant-breeding 



