284
J. A. KITCHING AND F. J. EBJXNG
from transplantation is combined with a clear demonstration of an inverse correlation in distribution between predator and prey, it is a
reasonable hypothesis that such a predator-prey relationship exists in
nature. To support such a proposal, we suggest that the following
criteria need to be fulfilled:
(a) the organism does not survive when transplanted to a site where
it does not normally occur, unless it is protected from predators
by cages.
(b) there is an inverse correlation between the distribution of the
organisms and the suspected predator, or alternatively, in the
places where it occurs the organism is inaccessible to the predator.
(c) the suspected predator is able to inflict lethal damage on the prey
in experiments in cages, or can be observed to do so in the
laboratory.
(d) there is direct evidence that the suspected predator is responsible
for destruction of the prey in transplantation experiments.
Our experiments on Nytilus, Paracentrotus and Thais have fulfilled
all, or nearly all, of these conditions. There remains the possibility that
in nature these organisms may fail, for quite different reasons, to develop in the situations from which they are missing, so that the opportunity for predation does not occur.
Successful survival of a species in spite of predation does not require
complete immunity for every individual. Production of a shell strong
enough to guarantee survival of all individuals would involve other
overriding disadvantages. All that is required is a sporting chance of
survival. For this reason there are likely to be fluctuations both in time
and space in the balance between predators and prey. This aspect of
the relationship will be developed, for Paracentrotus, in Section VIII.
VIII. SYNECOLOGY
As in other areas, it is possible to recognize a t Lough Ine a number
of communities of animals and plants, each in its characteristic habitat.
Naturally these communities are subject to local variation. It is the
aim of an ecologist to describe the system of food chains which operates
in each of these communities, to elucidate any changes, whether cyclical
or casual, in the populations of organisms within these communities,
and ultimately to describe the interactions of different species in quantitative terms. This last objective requires information as to the feeding,
growth, reproduction, and mortality, of all the important members of a
community over a range of conditions corresponding to those normally
experienced throughout the year in the area under consideration. At
present we do not know nearly enough about these matters, although
J. A. KITCHING AND F. J. EBJXNG
from transplantation is combined with a clear demonstration of an inverse correlation in distribution between predator and prey, it is a
reasonable hypothesis that such a predator-prey relationship exists in
nature. To support such a proposal, we suggest that the following
criteria need to be fulfilled:
(a) the organism does not survive when transplanted to a site where
it does not normally occur, unless it is protected from predators
by cages.
(b) there is an inverse correlation between the distribution of the
organisms and the suspected predator, or alternatively, in the
places where it occurs the organism is inaccessible to the predator.
(c) the suspected predator is able to inflict lethal damage on the prey
in experiments in cages, or can be observed to do so in the
laboratory.
(d) there is direct evidence that the suspected predator is responsible
for destruction of the prey in transplantation experiments.
Our experiments on Nytilus, Paracentrotus and Thais have fulfilled
all, or nearly all, of these conditions. There remains the possibility that
in nature these organisms may fail, for quite different reasons, to develop in the situations from which they are missing, so that the opportunity for predation does not occur.
Successful survival of a species in spite of predation does not require
complete immunity for every individual. Production of a shell strong
enough to guarantee survival of all individuals would involve other
overriding disadvantages. All that is required is a sporting chance of
survival. For this reason there are likely to be fluctuations both in time
and space in the balance between predators and prey. This aspect of
the relationship will be developed, for Paracentrotus, in Section VIII.
VIII. SYNECOLOGY
As in other areas, it is possible to recognize a t Lough Ine a number
of communities of animals and plants, each in its characteristic habitat.
Naturally these communities are subject to local variation. It is the
aim of an ecologist to describe the system of food chains which operates
in each of these communities, to elucidate any changes, whether cyclical
or casual, in the populations of organisms within these communities,
and ultimately to describe the interactions of different species in quantitative terms. This last objective requires information as to the feeding,
growth, reproduction, and mortality, of all the important members of a
community over a range of conditions corresponding to those normally
experienced throughout the year in the area under consideration. At
present we do not know nearly enough about these matters, although