Although there will always be a struggle for life between the individuals of the species, however few, already occupying any pond, yet as the number of kinds is small, compared with those on the land, the competition will probably be less severe between aquatic than between terrestrial species;
(a struggle for life between the individuals of the species, however few; occupying; any pond; T:already) (the number of kinds; is; small) (the competition; will probably be; less severe)
a struggle for life between the individuals of the species, however few the number of kinds the competition
occupying is will probably be
any pond T:already
small
less severe