XVI INTRODUCTION. 
tat a) This is the case with all and their peculia' 
habitats will be noticed when speaking of each 
species. This selection of situations, however 
is a physiological one, rather than one whic 
may be supposed to be the result of any intel' 
ligence in the animals themselves. For in th e 
same situations of climate and depth of water* 
the same species will frequently grow on any 
substances provided there are similarities 0 
surface. This is however considerably iuodifie 1 
by collateral circumstances, such as the powc 
to absorb and radiate heat and the durability 0 
the substances on which they grow. Thus f <Jl 
instance the Caryop/iyllia Smilhii most commonly 
selects for itself the moderately rough surface 1 ’ 
of stones, yet it has been repeatedly found in a 
young state on the lobes of Alcyunium digit a tun 1 ’ 
and on the stems of fnci, but in such situation* 
it never attains a full size. The young of all 
species w ill take root and grow for a short titf> e > 
in situations which afterwards appear to be d e =' 
truetive to them. Those ova therefore whic’ 
fix themselves in unfavourable situations peris* 1 ’ 
while others more favourably situated thrive an 
grow to perfection ; but slid it remains a matte 
for speculation, why one kind of locality shonh 
be more favourable to one species than to a ° 
other, since they derive no nutriment from tl) 
l’OOt. rj fl- 
it is a generally received opinion, that 
phytes do not inhabit the depths of the oce al1 ^ 
but are confined to shallow water and to distn (: 
surrounding the shores. The depths to wluc 
the coral reefs descend in the Lagoon islafl 
is not considered a contradiction to this opin ' 0 J 
since they are supposed to owe their position 
subsidences, in the same manner that the co' a 
in the hills of those islands are placed there ) 
