1899] PE NICECLEHOLUS IN HEREDITY 241 
germ-plasm is brought about by the extrusion of nucleoli, while the 
deficiency of chromatin, so often remarked in the nuclei of mature 
specialised cells, as compared with the large size of their nucleoli, 
would be a natural consequence of a reduction in the number of 
active, and an increase in the number of dormant, idioblasts, which 
might be expected to accompany specialisation if, as seems probable 
from the phenomena of vegetative regeneration, every mature cell 
must contain all the hereditary substance required for the develop- 
ment of an individual. 
Inheritance of Longevity. 
WALLACE, Weismann, and others have suggested that the normal 
lencth of life of organisms, which differs so much in different species, 
has been determined by natural selection. A creature lives as long 
as is good for the species. This was a general suggestioa—prompted 
partly by the strange irregularity and apparent capriciousness of the 
leneth of life in different animals—and the preliminary question was 
not raised, “Is longevity a heritable character?” This is obviously 
a very important question, since natural selection could not determine 
or fix the fit duration of life unless that character were inherited. 
We are indebted to Miss Mary Beeton and Professor Karl Pearson for 
a contribution towards the required answer. In a paper entitled 
“ A first study of the inheritance of longevity, and the selective death- 
rate in man,” read before the Royal Society of London on 15th June, 
the authors show that directly and collaterally duration of life is certainly 
inherited in the male line in man. They believe this to be the first 
quantitative measure of the inheritance of life’s duration. Further 
data for the inheritance of this character in the female line, and for 
the study of the inheritance of “brachybioty,” or short-livedness as 
distinguished from longevity, are being collected. The inquiry should 
be interesting to actuaries as well as to biologists. 
The second part of the paper is not less important. “In the 
presidential address at the Oxford meeting of the British Association 
we were told that no one had seen natural selection at work. In a 
criticism then published by one of us, it was suggested that every 
one who had examined a mortality table had seen natural selection at 
work. . . . All individuals die, but some, better suited by their con- 
stitution and characters to their environment than others, survive 
longer, and so are able, or better able, to reproduce themselves, and 
to protect for a longer time their offspring. To assert that natural 
selection does not exist, is to assert that the whole death-rate is non- 
selective, or is not a function of the constitution and characters of 
the individual. Looked at from this standpoint the existence of 
natural selection really becomes a truism. All that remains when we 
