106 REPORT OF THE CONFERENCE ON - GENETICS. 
(“force héréditaire’’). But this idea seems to me not only quite super- 
fluous but also wrong, the pretended different degrees of heredity 
being—in the cases hitherto analysed —the simple consequences of 
different types existing in the population erroneously regarded as 
homogeneous, but in reality containing individuals which are fluctuating 
about a plurality of types. 
I anticipate that the results of Lang’s researches will eventually 
prove to be quite reconcilable with my views. As to the experiments 
which have been tully carried through (with little-fluctuating types) he 
is a convinced Mendelian. But as to his experiments concerning snail 
populations with great fluctuations, experiments which are still only in 
their beginning, Lang seems to have been overpowered by the fluctua- 
tions. If the analysis can be carried to an end I cannot doubt that 
Lang will find distinct types as centres for transgressing fluctuations. 
The idea of “ degrees in heredity’’ was an advance in Vilmorin’s time, 
but now it only implies that the analysis has not been quite completed. 
In fact, wherever the essential difference between fluctuation and 
deviation of type (mutation included) is not conspicuous, we may be 
sure that a biological analysis has not been performed ; it may be that 
such analysis cannot be effected, or simply that the experimenters have 
neglected it. At all events I must again say emphatically that results 
as to which the analysis has not been fully performed, or cannot be 
effected, must never be used as a basis for fundamental biological 
theories. We have always to elucidate the unanalysed from the analysed 
facts ; the converse proceeding is wrong. 
The most interesting objection against my use of the principle of 
pure lines is made by Plate. It is that the variability will be diminished 
when intercrossing is excluded. lLotsy says something similar, if I 
have understood his somewhat ambiguous remarks. Plate, in his usual 
clear and sharp manner, expresses his thoughts about my little work. 
It seems to him that I have proved that self-fertilisation in few 
generations considerably diminishes the tendency to variation, and that 
a sort of fixed type is arising in the descent (“dass die Selbstbefruchtung 
die Neigung zum Variiren nach wenigen Generationen sehr erheblich 
nachlisst und sich gleichsam ein fester Typus der betreffenden Deszen- 
denten heranbildet’’). And Plate says further that the main result of 
my paper is an indirect proof.that intercrossing is a natural means for 
procuring variations (“ Das wichtigste Resultat, dass freilich in der 
ganzen Arbeit nirgends erwihnt wird, scheint mir darin zu liegen, dass 
sie indirekt beweist, dass Wechselbefruchtung ein natiirliches Mittel zur 
Krzeugung von Variationen ist”’). 
But Plate is here caught by misconceptions and prejudices, which he 
shares with others; zoologists being very often not familiar with the 
circumstances of natural self-fertilisation in plants. (The idea that 
self-fertilisation is something abnormal is very wide-spread; so a 
prominent anthropologist in a private letter expressed his opinion that. 
my beans in pure lines must soon die out! In nature self-fertilisa- 
tion may perhaps be more common in plants than cross-fertilisation, 
and Galton’s (22) own experiments stating his law of filial regression 
