356 
NALORE 
[AucusT 10, 1899 
the expiration of this lease the islands were relet for a period 
of twelve years to the North American Commercial Company, 
on more advantageous terms, the quota of skins being fixed for 
the first year at 60,000, while it has since been under the 
regulation of the Secretary to the Treasury. 
Putting aside for subsequent mention the question of pelagic 
sealing, it may be observed that between the years 1871 and 
1875 the number of breeding seals and young on the islands was 
estimated by Mr. Elliott, in round numbers, at 3,193,000. In 
spite, however, of the fact that this observer did not recognise 
that only a portion of the cows were on land at any one time, 
the Commission concludes that this estimate is far too high, and 
that 1,400,000 would have been a much closer approximation 
to the truth. They further state that between 600,000 and 
700,000 seems to be a fair estimate of the number of breeding 
females resorting annually to the islands between the years 1871 
and 1885; while at the present time (1896-97) the number is 
only about one fifth of what it then was. 
As regards the decline of the Pribyloff herd, the best evidence 
is afforded by the fact that whereas between the years 1871 and 
1885 no difficulty was experienced in obtaining the full number 
of 100,000 bachelor seals of the proper age before July 20, in 
1896 it was only found possible to obtain 30,000 fit for killing 
even by continuing the drives till July 27; while in the follow- 
ing year, when driving was carried on as late as August IT, only 
20,890 were obtained. It is largely on these data that the 
above-mentioned estimate of the former number of breeding 
animals is founded. 
The life of the female seal being estimated at from ten to 
fifteen years, thirteen years may be taken as an average, during 
ten of which she is capable of producing young. On this esti- 
mate 10 per cent. of the breeding females die of old age each 
winter, in addition to those which perish from other causes. The 
stock is replenished by the annual addition of the three-year-old 
females. Among the young and pups the death-rate from 
natural causes is very high; about two-thirds thus perishing 
annually before they attain the age of three years, when the 
females are fit for breeding and the males for killing. The 
most important of such natural causes are the presence of a 
parasitic worm on the sandy breeding-grounds, the trampling to 
death by the ordinary movements or fights of the adults, starv- 
ation of the pups from being separated from their mothers at a 
very early age, destruction by the killer-whale, and drowning 
‘during the winter storms. 
In 1896 the number of females with pups on the islands was 
about 157,000, and in the following year 130,000. In certain 
rookeries the number of pups had diminished from about 16,240 
in 1896 to about 14,320 in 1897, indicating a decrease of about 
12 per cent., the number of harems having likewise diminished 
by about 10} percent. Although precise figures are not avail- 
able, the total decrease in the number of breeding females for the 
same period may be put down at about 15 per cent., and that of 
the males fit for killing at about 30 per cent. 
Although the exact number to which it is safe to reduce the 
breeding bulls in a rookery as compared to the cows has not yet 
been ascertained, it is quite certain that in the Pribyloff herd 
(here is no reduction of the former to anything near that limit. 
Consequently the killing carried on in the islands cannot be held 
responsible for the serious reduction which has of late years 
taken place in the numbers of the herd. On the contrary, such 
thinning out of the bachelors has tended to the actual increase 
of the breeding herd, owing to the less amount of fighting 
which takes place when the bulls are reduced in number, and 
the consequent diminished loss of life among the cows and pups 
‘owing to such, fights. 
On the other hand, there is every reason for believing that the 
‘waning of the herd is solely to be attributed to pelagic sealing, 
in which the number of females taken is very largely in excess 
of the males, while for each female so killed an unborn pup is 
also destroyed, and in the case of those which have already bred 
a second pup is starved miserably to death on land. Since the 
normal rate of increase of the breeding herd is a little short 
of 17 percent., while the natural death-rate from old age is 
not far from ro per cent., it follows (without allowing for 
other natural causes of death among the adults) that not more 
than about 6-2/3 per cent. of the females can be destroyed by 
human agency year by year without involving the ultimate 
destruction of the herd. This limit has been very largely ex- 
ceeded as the result of pelagic sealing, in which (in spite of 
statements to the contrary) it is impossible to distinguish 
NO. 1554, VOL. 60] 
females from males until too late; and in consequence of this 
the Pribyloff herd has been so reduced that neither pelagic nor 
land sealing yields an adequate profit on the money invested. 
The Commission, indeed, go so far as to say that from a com- 
mercial point of view the herd is virtually destroyed. ‘* But 
this,” they add, ‘‘ has not involved the biological destruction 
of the herd. Under wise protection it may regain its former 
numbers.” That such protection (which involves the prohibition 
of the killing of females, and therefore apparently also of 
pelagic sealing!) may be extended to the herd while there is 
yet time, must be the hope of every naturalist. Res 
INHERITANCE OF LONGEVITY IN MAN. 
“THE object of this paper? is twofold, namely :— 
(1) To ascertain whether duration of life is inherited, and 
(2) To exhibit natural selection at work in man. 
According to both Wallace and Weismann the duration of 
life in any organism is determined by natural selection. An 
organism lives so long as it is advantageous, not to itself, but 
to its species that it should live. But it would be impossible 
for natural selection to determine the fit duration of life, as 
it would be impossible for it to fix any other character, unless 
that character were inherited. Accordingly a preliminary in- 
quiry as to whether duration of life is inherited or not seems 
needful before we consider further the plausibility of Wallace 
and Weismann’s hypothesis. The present paper shows that 
directly and collaterally duration of life is certainly inherited 
in the male line. We 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 shortlived- 
ness as distinguished from longevity are now being collected. 
We point out in the paper and endeavour to illustrate by examples 
the importance of such quantitative measure of the inheritance 
of life’s duration for actuarial practice. 
The second aim of our paper seems to us, perhaps, to 
have the greater scientific importance. 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 sug- 
gested that every one who had examined a mortality table 
had seen natural selection at work. Now the meaning of 
natural selection is absolutely simple. All individuals die, but 
some, better suited by their constitution 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 
period 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 desire to see it at work is to determine the relative 
amounts of the selective and non-selective parts of the death- 
rate for individuals living under the like environment. If, 
therefore, individuals living under much the same conditions 
are dealt with, the determination of the selective and non- 
selective death-rates isa measure of the quantitative amount of 
natural selection. Now we can answer this problem in two 
ways. First we may take any organ, and determine whether 
the death-rate is a function of the size of this organ. This 
method, adopted by Prof. Weldon, would be the direct and 
best method, if the results were not apt to be screened by other 
factors. In the first place we have to hit upon some organ 
upon which vitality largely and sensibly depends ; and 
this is not easy, for constitutional power of resisting 
the attacks of disease may depend upon, not one organ, but on 
the complex relationships of a system of organs, and in the next 
place the whole problem is rendered difficult by changes due to 
growth. Inthe second method we do not attempt to select 
any organ whatever, but select individuals having any general 
1 The writer takes this opportunity of mentioning that, misled by a 
summary of some of the evidence given before the Paris Commissién, he 
was inclined in the ‘‘ Royal Natural History” to pronounce pelagic sealing 
more humane than seal-killing on land. 
2 “Data for the Problem of Evolution in Man. II. A First Study of the 
Inheritance of longevity and the Selective Death-rate in Man.” By Miss 
Mary Beeton and Karl Pearson, F.R.S., University College, London. 
Received May 29. (Abstract of a paper read before the Royal Society, 
June 15.) 
