190 SECTIONAL ADDRESSES. 



Pi pollen grains are all long, yet half of them carry the factor for 

 roundness. If we take the chromosome view, and if it be presumed 

 that the factor for roundness is not segregated until the reduction 

 division, the cytoplasm of the pollen mother cells may be supposed to 

 act as a foreign medium owing to a mixtm-e of qualities having been 

 impressed upon it through the presence of the two opposite allelomorphs 

 before the moment of segi'egation. We should consequently infer that 

 the round pollen shape is only produced when the round-factor-bearing 

 chromosome is surrounded by the cytoplasm of an. individual which 

 does not contain the long factor. If, further, we regard the result in 

 this case as indicative of the normal inter-relation of nucleus and 

 cytoplasm in the hereditary process, we shall be led to the view that 

 whatever the earlier condition of mutual equilibrium or interchange 

 between these two essential cell constituents may be, an ultimate stage 

 is reached in which the role of determining agent must be assigned to 

 the nucleus. To pursue this theme farther, however, in the present 

 state of our knowledge would serve no useful purpose. 



Before bringing this Address to a conclusion I may be permitted to 

 add one word of explanation and appeal. In my remarks I have 

 deliberately left on one side all reference to the immense practical 

 value of breeding experiments on Mendelian lines. To have done so 

 adequately would have absorbed the whole time at my disposal. It is 

 unnecessary to-day to point out the enormous social and economic gain 

 following from the application of Mendelian methods of investigation 

 and of the discoveries which have resulted therefrom during the last 

 twenty years, whether we have in mind the advance in our knowledge 

 of the inheritance of ordinary somatic characters and of certain patho- 

 logical conditions in man, of immunity from disease in races of some 

 of our most important food plants, or of egg-pi'oduction in our 

 domestic breeds of fowls. 



My appeal is for more organised co-operation in the experimental 

 study of Genetics. It is a not uncommon attitude to look upon the 

 subject of Genetics as a science apart. But the complex nature of the 

 problems confronting us requires that the attacking force should be a 

 composite one, representing all arms. Only the outworks of the 

 fortress can fall to the vanguard of breeders. Their part done, they 

 wait ready to hand over to the cytologists with whom it lies to con- 

 solidate the position and render our foothold secure. This accom- 

 plished, the way is cleared for the main assault. To push this home 

 we urgently need reinforcements. It is to the physiologists and to the 

 chemists that we look to crown the victory. By their co-operation 

 alone can we hope to win inside the citadel and fal^hom the meaning of 

 those activities which take shape daily before our eyes as we stand 

 without and observe, but the secret of which is withheld from our 



