482 
the genes, or particles of the chromosomes, the chances of the 
combinations of characters that are necessary arising in the 
necessary consecutive order, without any inimical combinations, 
are so enormous that one’s faith falters, and one turns to seek 
a solution which requires a smaller draft upon our credulity. 
That similar sequences should have occurred two, three, or more 
times quite independently is still harder to believe. This has 
been aptly called the “lucky throw of the Mendelian dice,” but 
the dice are not six-sided, but very many-sided, and many sides 
bear death upon their face, and others bear indifference, and 
among the remainder only certain sequences are allowable, and 
the banker is Death and Oblivion. 
But even to those whose faith is greater than mine there are 
other obstacles. While there is a large amount of negative evi- 
dence to support Weismann, there is also some positive evi- 
dence which is against him. That the continuity of the germ 
plasm is not so universal as he thought, is evident from work 
such as Gatenby’s on the formation of new egg cells during 
sexual maturity in frogs. Kammerer’s work cannot be ignored 
by his opponents, and the work of Guyer and Smith on the eyes 
of rabbits is a strong point against him. The more recent work 
of Garrett and Harrison on melanism among British moths is 
of great interest, for here we find that melanism caused by cer- 
tain metal salts is inherited, and follows the Mendelian law.* 
Turning to the other school of thought, we find few today 
who hold the crude views of a past generation. Early in the 
development of animal life a mechanism must have been devel- 
oped to guard against individual mutilations becoming incorpo- 
rated into the race, otherwise we should have nothing but 
maimed and helpless races of animals. 
Fortunately, we have a few leaders who can see the virtues 
and vices of both of these extreme schools of thought, and who 
are combining the best in each into a more workable theory. 
In the study of the development of the phylum, as well as the 
individual, the great task is to discover the mechanism by which 
similar cells develop into totally different organs, having vastly 

* Melanism in the Lepidoptera and its Possible Induction, Nature, 
August, 1923, p. 240. See, also, Nature, September 16, 1922, p. 380. 
