138
R. J.
GOSS
pigmentation. Regenerated tails are covered by smaller and more
numerous scales than in the stump, and are more heavily pigmented,
especially during development. Thus, in many respects, the regenerating
lizard tail represents a departure from the morphological pattern of the
stump. In the absence of much experimental information concerning
the morphogenesis of tail regeneration in the lizard, one can only
speculate on the significance of the anatomical discrepancies between
the old and the new tissues. It is safe to assume that structure always
reflects function, and that one of the main functions of the lizard tail is
to immolate itself to predators by autotomy, in order to facilitate the
lizard's escape. The main purpose of tail regeneration may well be to
replace the lost part as quickly as possible in order to have something
to be sacrificed again, should the need arise. Whether or not the new tail
is an exact replica of the old would seem to be of secondary importance;
indeed, it need not even be motile, so long as it can be rapidly reproduced
and still represent a reasonable facsimile of the original. Thus, the more
important expedient of rapid growth may have been favoured by
selective pressures at the expense of the precise replication of the tail
by the regenerate, but unfortunately it cannot be determined if accelerated growth is promoted by the morphological divergence of the tail
regenerate. In view of its hypomorphic nature, the serious analysis of
morphogenetic factors in the regenerating lizard tail might prove
rewarding.
A final example of morphogenetic disparity between the original
appendage and the regenerate which supplants it are the annual changes
in the form of deer antlers. Commensurate with the increasing age of the
buck, the successive sets of antlers normally become larger and exhibit
more branches. When the final mature size of the animal is attained, the
character of subsequent antlers usually remains relatively unaltered
until the hormonal changes of old age bring about the antler abnormalities associated with senility. The increments in the antlers of
growing bucks do not represent a true morphogenetic change; rather,
they appear to be natural extensions of the original growth pattern in
the antler. The final configuration is a function of how much antler
tissue is grown: if only a small amount is produced, a spike antler
results; greater quantities of antler tissue develop into increasingly
elaborate specimens. The amount of antler material produced is contingent upon the duration of the growing season, which in turn depends
upon its date of onset. Young deer commence growth of their antlers
relatively late in the season (e.g., late spring or even early summer),
while older bucks lose their antlers and begin the growth of new ones
sooner, sometimes in winter. Moreover, the areas of the basal pedicles
from which antlers grow are proportional to the overall size of the
R. J.
GOSS
pigmentation. Regenerated tails are covered by smaller and more
numerous scales than in the stump, and are more heavily pigmented,
especially during development. Thus, in many respects, the regenerating
lizard tail represents a departure from the morphological pattern of the
stump. In the absence of much experimental information concerning
the morphogenesis of tail regeneration in the lizard, one can only
speculate on the significance of the anatomical discrepancies between
the old and the new tissues. It is safe to assume that structure always
reflects function, and that one of the main functions of the lizard tail is
to immolate itself to predators by autotomy, in order to facilitate the
lizard's escape. The main purpose of tail regeneration may well be to
replace the lost part as quickly as possible in order to have something
to be sacrificed again, should the need arise. Whether or not the new tail
is an exact replica of the old would seem to be of secondary importance;
indeed, it need not even be motile, so long as it can be rapidly reproduced
and still represent a reasonable facsimile of the original. Thus, the more
important expedient of rapid growth may have been favoured by
selective pressures at the expense of the precise replication of the tail
by the regenerate, but unfortunately it cannot be determined if accelerated growth is promoted by the morphological divergence of the tail
regenerate. In view of its hypomorphic nature, the serious analysis of
morphogenetic factors in the regenerating lizard tail might prove
rewarding.
A final example of morphogenetic disparity between the original
appendage and the regenerate which supplants it are the annual changes
in the form of deer antlers. Commensurate with the increasing age of the
buck, the successive sets of antlers normally become larger and exhibit
more branches. When the final mature size of the animal is attained, the
character of subsequent antlers usually remains relatively unaltered
until the hormonal changes of old age bring about the antler abnormalities associated with senility. The increments in the antlers of
growing bucks do not represent a true morphogenetic change; rather,
they appear to be natural extensions of the original growth pattern in
the antler. The final configuration is a function of how much antler
tissue is grown: if only a small amount is produced, a spike antler
results; greater quantities of antler tissue develop into increasingly
elaborate specimens. The amount of antler material produced is contingent upon the duration of the growing season, which in turn depends
upon its date of onset. Young deer commence growth of their antlers
relatively late in the season (e.g., late spring or even early summer),
while older bucks lose their antlers and begin the growth of new ones
sooner, sometimes in winter. Moreover, the areas of the basal pedicles
from which antlers grow are proportional to the overall size of the