Heredity in Plants, Animals, and Man. 
Being the Presidential Address delivered before the 
Plymouth Institution, October 12th, 1916. 
By 
E. J. Allen, D.Sc., F.RBS., 
Director of the Plymouth Laboratory. 
[Reprinted from the Transactions of the Plymouth Institution. ] 
With Diagrams 1-11 in the Text. 
Or the many branches of biological enquiry which have occupied the 
attention of naturalists during the last twenty years the one which has 
perhaps yielded the most striking results, from a theoretical point of view, 
has been the study of heredity in plants and animals—the study of the 
laws according to which the characters of parents are transmitted to their 
descendants. 
The practical achievements of the farmer, the gardener, and the 
animal breeder in obtaining and fixing innumerable varieties of cultivated 
plants and domesticated animals had made everyone familiar with the 
general facts that variations occur, and that these variations sometimes 
are and sometimes are not transmitted from parent to offspring. Common 
observation of the men, women, and children with whom we come in 
contact shows us that human beings algo exhibit similar phenomena. 
Amongst a family of children several quite distinct types of feature, of 
build, of colour of hair or eye are found, and it is often quite plain from 
which parent, or from the family of which parent, a particular charac- 
teristic has been derived. The same thing is sometimes clearly true of 
mental and moral traits. 
Charles Darwin, especially in his work “‘ On the Variations of Animals 
and Plants under Domestication,” brought together a great collection of 
facts bearing on this subject, which formed the basis upon which his 
theory of natural selection was built up. Around the question of the 
cause or origin of such variations much discussion has centred. Darwin 
hin-self was inclined to favour the view generally associated with the 
