88 



NATURE 



[September 15, 192 1 



In the first place it seems to be purely a matter 

 of chance what luck the germ-cells have in their 

 mating, what particular ovum is fertilised by what 

 particular spermatozoon, and, owing to the enor- 

 mous numbers in which ova and spermatozoa are 

 produced, the possibilities may be almost infinite. 

 In the second place there are many alternative 

 possibilities with regard to the particular factors 

 which any given germ-cell, male or female, may 

 contain. This depends upon which particular 

 chromosomes happen to remain in the germ-cell 

 after the double number has been halved again. 

 In animals this halving takes place at the time 

 when the germ-cells are ripening, shortly before 

 they are ready to unite in the fertilised ^%^. The 

 maternal and paternal chromosomes in each, differ- 

 ing as regards the factors they contain, pair off 

 during the process of mitosis. The members of 

 each pair then separate, and one of them alone 

 remains in each mature germ-cell. Hence the 

 germ-cells, even of the same individual, come to 

 differ amongst themselves to a practically un- 

 limited extent as regards their factorial constitu- 

 tion. The life of the individual is like a game of 

 cards, in which a very great deal depends upon 

 the shuffling of the pack, and the player has to 

 do the best he can with the hand dealt out to him. 

 He may make a hopeless failure of it, or a great 

 success ; but still the stream of life flows on, ever 

 gathering and combining new experiences, ever 

 forming itself into fleeting individualities and leav- 

 ing them to perish on its banks as it passes on to 

 fresh attempts at self-expression. 



The interest of the Mendelian breeding experi- 

 ments is so absorbing that it is little wonder if 

 more fundamental aspects of the problem of 

 heredity, to which we have alluded in the earlier 

 part of our lecture, have been largely lost sight of 

 in recent years, while the factorial hypothesis has 

 been hailed by some extremists as the all-suflficient 

 explanation of everything. The characters of the 

 organism may indeed be modified by factors in 

 the germ-plasm, just as the character of a loaf 

 may be modified by putting caraway seeds into 

 the dough ; but the caraw'ay seeds do not explain 

 the loaf, and the Mendelian factors cannot ex- 

 plain the organism as a whole. There is doubt- 

 less a good deal of truth in the old saying that 

 life is made up of trifles ; but it is not the whole 



truth, and the body of a living organism cannot 

 be regarded as merely the sum-total of its unit 

 characters. 



Whatever may be their significance from the 

 j point of view of the general theory of evolution 

 I and heredity, however, there can be but one 

 ! opinion as to the immense practical importance of 

 the Mendelian investigations. They have already 

 led to the production of many valuable forms of 

 life, more especially plants, that are to all intents 

 and purposes new creations, although their value 

 and novelty may depend merely upon the bringing 

 together of desirable characters in new combina- 

 tions and the elimination of undesirable features. 



Nor are the possibilities of improvement by 

 selective mating confined to our domesticated 

 plants and animals. Hopes are entertained bv 

 many enthusiasts, banded together in the interests 

 of what they have thought fit to term the science 

 of Eugenics, of effecting vast improvements in the 

 human race itself by the application of Mendelian 

 principles. It does not seem likely, however, or 

 even desirable, that men and women should ever 

 consent to be guided in their choice of mates by 

 purely utilitarian considerations. 



There are many objections to any far-reaching 

 schemes of this kind, but it does seem possible, 

 when once the facts of heredity are generally 

 known, that the exercise of an enlightened public 

 opinion and individual choice may result in the 

 elimination from the stream of human life of many 

 heritable characteristics which it is very unde- 

 sirable to perpetuate. In extreme cases, such as 

 feeble-mindedness and certain forms of insanity, 

 it may even be necessary for the community to 

 protect itself by legislation against the criminal 

 propagation of the unfit. 



What is wanted, first and foremost, however, 

 is education, and I trust that you will agree with 

 me that it is education in biology — the science of 

 life — to which we may most hopefully look for the 

 physical and mental improvement of the human 

 race. Men and women must learn to realise their 

 responsibilities towards future generations from 

 the biological point of view, and it is in this direc- 

 tion that the citizens of a great city like Edinburgh 

 can best help, by generously supporting the cause 

 of education and research as represented by your 

 ancient and world-famed University. 



Speech through the iEther.^ 



By Sir Oliver Lodge, F.R.S. 



AN intelligent deep-sea fish would disbelieve in 

 water. It would be too uniform and omni- 

 present to make any impression on its senses. 

 Near the surface it might encounter waves and 

 currents, but to creatures thoroughly embedded 

 in its depths water would make no display. Such 

 is our own condition with regard to the aether of 

 space. It eludes direct perception ; its existence 



1 Abstract of a citizens' lecture of the British Association delivered at 

 Edinburgh on September 6. 



cannot be directly demonstrated ; it has to be 

 inferred. 



The fish would probably also disbelieve in 

 gravity, since it would not experience it, and 

 some of the hyperintelligent among us, for quite 

 another reason, seem to be following its example ; 

 but that is another story. Suffice it to say that 

 direct sensation is but a poor clue to reality unless 

 supplemented by a great deal of reasoning and 

 indirect inferences. Our senses tell us only about 



NO. 2707, VOL. 108] 



