October, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



555 



segregation ■ have since been found to be, it must not 

 be supposed that they are universal. Already one or 

 two cases are known in which a more complex form of 

 segregation takes place, which seems to point to a reso- 

 liilion of compound characters introduced by the parents 

 into a series of characters which, perhaps, may be sus- 

 ceptible of recombination, by means of suitable matings, 

 into the original compound character. + 



Nor does dominance occur universally. Speaking 

 generally, the union of gametes bearing the different 

 members of a pair of characters results in the forma- 

 tion of a hybrid whose character may be : — 



(i) Indistinguishable from that of one of the 

 parents. 



(2) Intermediate between the characters of the 



parents. 



(3) Unlike either of the characters of the parent. 

 The first result is that of simple dominance; in the 



second and third dominance is absent. When a hybrid 

 of cither of the last two types is self-fertilised, we are 

 able to distinguish the offspring which result from the 

 union of unlike gametes from the remainder, and thus 

 the ratio of 



iDD: 2DR : iRR 



among these offspring is at once appreciable (compare 

 table p. 554)- Finally, cases are known in which domi- 

 nance is irregular, the offspring sometimes resembling 

 cne parent, sometimes the other. What determines 

 the dominance in such cases is quite unknown, and it 

 will be seen at once that the work is attended with 

 great difficulty owing to the impnssibilitv of recognis- 

 ing the constitution of any indi\idual from its appear- 

 ance. 



In conclusion, attention must be drawn to the close 

 parallel which exists, as Bateson pointed out in 1894, 

 between the phenomenon of discontinuous variation and 

 that of sex. There follows at once the question as to 

 whether the sex-characters may not undergo segrega- 

 tion in the formation of the gametes of the male, or 

 female, or both. A crucial experiment is still wanting, 

 but indirect evidence is accumulating which steadily 

 poinis toward an affirmative answer to the question. 



It is not possible to go further into detail in this 

 paper; enough has, I think, been said to indicate the 

 principles of the Mendelian method. The offspring of 

 each individual is treated separately, nor does one as- 

 sume that any two individuals of like descent are simi- 

 larly constituted until the analysis, carried out by the 

 experiment of breeding from them, has proved them to 

 be so. That is to say, it is not simply through a know- 

 ledge of the ancestry of an indi\idual that we can cer- 

 tainly di'lermine its nature, but by a knowledge of its 

 posterity. 

 R.P. G. 



* The production by the cross-bred of gametes pure in respect 

 of one or other member of each pair of characters. 



t Since the above was written it has been found that some, at 

 any rate, of the cases referred to here are examples of a phenome- 

 non of Rreat interest. It is now clear that wliat appears to be a 

 third distinct form may be due to the presence simultaneously 

 of certain members of two definite allclomorphic pairs. For 

 instance, in Fiimula sinensis astrain islnown which is characterised 

 by the e.\tensive spreading of tlie central yellow eye. All the'e 

 "yellow flush" plants are in the condition called by Darwin 

 " ciliial-styled." Experiment shows that tlie yellow flush is an 

 ordinary recessive character, the cominon non-fliished type being 

 dimiinant. The flush is transmitted independently of the length 

 of style, and may be transferred to tlie sliort-styled or llirum type. 

 Yet when the flush is developed in plants which by ganietic 

 composition would be long-styled, the style does not pass tlirough 

 tlie antliers, and the equal-styled form is produced. 



The International 

 Hybridization and 



Conference on 

 Plant-breeding. 



The organisers of the third International Conference 

 on Hybridization, held at Westminster under the 

 auspices of the Royal Horticultural Society, must be 

 heartily congratulated on the great success which at- 

 tended the meeting. It was a fortunate circumstance 

 that so many distinguished foreign guests were able to 

 accept the Society's invitation, so that the scientific 

 and practical workers of this country had the pleasure 

 of welcoming representatives froin Denmark, Germany, 

 Austria, and France, as well as from the United States 

 and Canada. 



Since the first Conference was held at Chiswick in 

 1898, almost revolutionary advances have been made 

 in the study of heredity and variation. It is difficult 

 to realise that only six years ago Mendel's work was 

 still buried in the obscurity where it had lain for 35 

 years. The scarcely less important discoveries of 

 de \'ries, on the origin of species by Mutation, are of 

 still more recent date. No better instances can be cited 

 than those of the successful unravelling of problems 

 in heredity and variation by means of the exhaustive 

 study of a special case. In this method lies the key to 

 the progress which has been made, and to the solution 

 of further problems in the future. 



In opening the proceedings of the Conference the 

 President, Mr. Bateson, contrasted the present state of 

 our knowledge of heredity with that which obtained at 

 the first Conference eight years ago. .-\t that time the 

 predominant note was mystery ; now we speak less of 

 mystery and more of order; systematic research has 

 now replaced work that could only be carried on in the 

 dark, along ill-defined lines. Mr. Bateson proceeded 

 briefly to discuss some of the practical and theoretical 

 results of the Mendelian laws. He show'ed that we 

 have now a clear conception of the meaning of." pure- 

 bred," a pure-bred individual being one which develops 

 from the union of two cells, male and female, which are 

 alike in composition, in that they bear identical 

 characters. In the same way Reversion may be ex- 

 plained as the meeting once more of characters long 

 separated, and, conversely. Variation is often the visible 

 sign of separation, or segregation into different germ 

 cells, and thence into different individuals, of charac- 

 ters which have hitherto been known only in combina- 

 tion with one another. The disco\eries of .Mendel 

 have made it possible to subject the work of the 

 hybridist to precise investigation, and often suggest 

 the course which should be pursued in the attempt to 

 create and fix desirable types, a course which is not 

 always, by any means, that which unaided common 

 s.-nse might suggest. The great advances in the ap- 

 plication of science to practical use have generally be- 

 come possible through discoveries made in the pursuit 

 of knowledge as an end in itself, without ulterior pur- 

 pose, and it is to work carried on in this spirit that we 

 should look for future results. 



Of the numerous papers which wcie read before tin- 

 Conference, one of the most interesting was that in 

 which Miss Saunders described her experiments upon 

 Stocks (Matthiola). The flower-colour in Stocks, as 

 in Sweet Peas, has been found to depend upon the 

 siiiittllancous presence in one individual of two 



