358
P. 5. MEADOWS AND J. I. CAIWBELL
larvae to their physical environment have not been considered
as they are listed by Williams (1964, 1966). Many larvae are
gregarious, and settle near adults of their own species in response
to species specific chemicals present on or possibly emanating
from the adults. The chemical nature of the substances has
been studied. The mobile adults of some species of marine
and freshwater invertebrates are gregarious. One or two species
change their behaviour when near other members of their
own species ; these changes increase the probability of aggregations forming ; we have therefore termed the phenomenon
indirect gregariousness.
(b) The larvae and adults of some species of aquatic invertebrates,
most of which are also gregarious, maintain a minimum
distance from each other (space out), while the adults of others
show well d e h e d aggressive behaviour. Spacing out behaviour
may be related to the secretion of repellent chemicals. The
interaction of gregarious and spacing out behaviour has not
been investigated.
(c) The larvae of marine invertebrates that occur on seaweeds can
recognize their preferred seaweed by species specific chemicals.
Some species of seaweed appear to contain inhibitory chemicals.
Many freshwater invertebrates live on or in plants, but few of
these associations have been analysed.
(d) Marine larvae that settle under experimental conditions in
response to chemicals which are specific either to their own
adults or to a particular species of seaweed, seem in most
instances to detect the chemicals only after contact with
the solid surfaces to which the chemicals are adsorbed.
(e) The larvae of adults of burrowing intertidal and marine invertebrates recognize their characteristic sediments in part by
the nature of the associated microbial fauna; this fauna can be
extremely complex but has only been studied in detail on sand
grains.
(f) Micro-organisms form a film on flat surfaces in fresh waters
and in the sea. The larvae of sedentary marine invertebrates
have a confusing array of responses to this a m .
(9) Nothing is known of the responses of freshwater invertebrates
to the microbial fauna of sediments or to the microbial film on
flat surfaces.
(A) The food preferences of mobile herbivorous and carnivorous
species, and the responses of prey species to their predators,
P. 5. MEADOWS AND J. I. CAIWBELL
larvae to their physical environment have not been considered
as they are listed by Williams (1964, 1966). Many larvae are
gregarious, and settle near adults of their own species in response
to species specific chemicals present on or possibly emanating
from the adults. The chemical nature of the substances has
been studied. The mobile adults of some species of marine
and freshwater invertebrates are gregarious. One or two species
change their behaviour when near other members of their
own species ; these changes increase the probability of aggregations forming ; we have therefore termed the phenomenon
indirect gregariousness.
(b) The larvae and adults of some species of aquatic invertebrates,
most of which are also gregarious, maintain a minimum
distance from each other (space out), while the adults of others
show well d e h e d aggressive behaviour. Spacing out behaviour
may be related to the secretion of repellent chemicals. The
interaction of gregarious and spacing out behaviour has not
been investigated.
(c) The larvae of marine invertebrates that occur on seaweeds can
recognize their preferred seaweed by species specific chemicals.
Some species of seaweed appear to contain inhibitory chemicals.
Many freshwater invertebrates live on or in plants, but few of
these associations have been analysed.
(d) Marine larvae that settle under experimental conditions in
response to chemicals which are specific either to their own
adults or to a particular species of seaweed, seem in most
instances to detect the chemicals only after contact with
the solid surfaces to which the chemicals are adsorbed.
(e) The larvae of adults of burrowing intertidal and marine invertebrates recognize their characteristic sediments in part by
the nature of the associated microbial fauna; this fauna can be
extremely complex but has only been studied in detail on sand
grains.
(f) Micro-organisms form a film on flat surfaces in fresh waters
and in the sea. The larvae of sedentary marine invertebrates
have a confusing array of responses to this a m .
(9) Nothing is known of the responses of freshwater invertebrates
to the microbial fauna of sediments or to the microbial film on
flat surfaces.
(A) The food preferences of mobile herbivorous and carnivorous
species, and the responses of prey species to their predators,