Nov., 1890. 
ORGANIC DEATH. 
241 
ORGANIC DEATH.* 
BY F. T. MOTT. 
PRESIDENT OF THE MIDLAND UNION OF NATURAL HISTORY SOCIETIES. 
We are accustomed to take for granted that organic life 
implies organic death ; that every living thing if let alone will 
die of itself; that in each species there is an average limit of 
life, and that no individual of that species can much exceed 
that limit. 
To some extent this doctrine has been disputed. I pro¬ 
pose to consider the question, whether it is founded upon 
sufficient evidence. 
Do things die, or are they always killed ? 
It has been pointed out that unicellular organisms which 
propagate by fission are practically immortal; that under 
normal conditions they simply grow and divide, that each 
division grows and divides again, and that this process 
may go on ad libitum without any approach to death. Weis- 
mann asserts that the germ-cells of the higher animals are 
of this immortal nature, and that whereas the somatic or 
body cells necessarily and entirely perish with the death of 
the individual, the germ substance is passed on from genera¬ 
tion to generation. It is an axiom in mechanics that a body 
once set in motion will continue to move in the same 
direction, and with uniform velocity, until something stops it 
or turns it aside. Mechanical forces do not die: they are 
always killed. If organic forces are of the same nature, it 
would seem probable that the same law applies to them. 
Glancing down the pages of organic history we observe 
that numbers of families, genera, and species have appeared 
at various epochs, have increased in numbers, in size, and in 
variety, and have at some subsequent epoch decreased and 
finally disappeared. There are two possible explanations of 
this fact. Each of these groups may have come into existence 
with a certain definite life period intrinsically belonging to it 
by reason of the nature of its originating force: a certain career 
which it must go through; ur, each group may have been simply 
crushed out of existence by the development of stronger com¬ 
peting forms, or starved to death by a gradual change of 
climate. The tendency of modern evolutionary science is to 
accept the second explanation ; to believe that genera and 
species do not die of themselves, have no intrinsic tendency 
*Read at the Annual Meeting of the Midland Union of Natural 
History Societies, held at Leicester, September 18th, 1890. 
