118
R.
J.
GOSS
assumption that the potentialities of blastemas are limited to the
specific kinds of appendages from which they originate.
Although the kind of regenerate destined to develop may be inherent
in the blastema cells, there is compelling evidence that within a given
blastema the fates of individual cells are originally undetermined. One
can, for example, completely disrupt the mass of undifferentiated cells
in a young blastema with a fine needle, yet such scrambled blastemas
nevertheless develop into normal regenerates. This kind of experimental
result, coupled with other data mentioned elsewhere (Section V, A, 3),
indicates that the differentiation of blastema cells is, in large part,
determined by their positions in relation to the stump tissues. The latter,
however, despite various defects, are capable of remarkable regulatory
capacities in directing the morphogenesis of blastemas (Section VI).
V. Morphogenetic Influence of the Stump
Inasmuch as regenerates exhibit spatial relationships commensurate
with the anatomical arrangements of tissues in the stumps from which
they originate, it is concluded that morphological organization is conferred upon the differentiating blastema by communication with the
tissues in the subjacent stump. Thus, the problem of morphogenesis in
such a system includes the analysis of (a) what tissues in the stump are
necessary for the initiation and the sustained growth of regeneration
and (6) which ones are essential for the development of normal, fully
organized regenerates.
Inseparable from these aspects of the problem is the consideration of
the remarkable regulatory capacity exhibited by regenerates developing
from abnormal stumps. Although some deficiencies in an appendage do
not interfere with the subsequent development of normal structures in
place of amputated ones, certain other experimental interventions in the
stump are reflected in corresponding alterations in the morphogenesis
of the resulting regenerate. By comparing the extents to which the
organisation of regenerates is altered by various kinds of injuries to the
appendages from which they were produced, it has been possible to
establish which component tissues of the stump play active roles in
directing the morphogenesis of regenerating parts.
A. Roles of Individual Tissues
Experimental treatments designed to analyse the influences of specific
stump tissues on the morphogenesis of regenerates may be classified into
various categories: (1) simple deficiency experiments, e.g., depriving the
appendage of specific kinds of tissue; (2) the addition of extra tissues;
R.
J.
GOSS
assumption that the potentialities of blastemas are limited to the
specific kinds of appendages from which they originate.
Although the kind of regenerate destined to develop may be inherent
in the blastema cells, there is compelling evidence that within a given
blastema the fates of individual cells are originally undetermined. One
can, for example, completely disrupt the mass of undifferentiated cells
in a young blastema with a fine needle, yet such scrambled blastemas
nevertheless develop into normal regenerates. This kind of experimental
result, coupled with other data mentioned elsewhere (Section V, A, 3),
indicates that the differentiation of blastema cells is, in large part,
determined by their positions in relation to the stump tissues. The latter,
however, despite various defects, are capable of remarkable regulatory
capacities in directing the morphogenesis of blastemas (Section VI).
V. Morphogenetic Influence of the Stump
Inasmuch as regenerates exhibit spatial relationships commensurate
with the anatomical arrangements of tissues in the stumps from which
they originate, it is concluded that morphological organization is conferred upon the differentiating blastema by communication with the
tissues in the subjacent stump. Thus, the problem of morphogenesis in
such a system includes the analysis of (a) what tissues in the stump are
necessary for the initiation and the sustained growth of regeneration
and (6) which ones are essential for the development of normal, fully
organized regenerates.
Inseparable from these aspects of the problem is the consideration of
the remarkable regulatory capacity exhibited by regenerates developing
from abnormal stumps. Although some deficiencies in an appendage do
not interfere with the subsequent development of normal structures in
place of amputated ones, certain other experimental interventions in the
stump are reflected in corresponding alterations in the morphogenesis
of the resulting regenerate. By comparing the extents to which the
organisation of regenerates is altered by various kinds of injuries to the
appendages from which they were produced, it has been possible to
establish which component tissues of the stump play active roles in
directing the morphogenesis of regenerating parts.
A. Roles of Individual Tissues
Experimental treatments designed to analyse the influences of specific
stump tissues on the morphogenesis of regenerates may be classified into
various categories: (1) simple deficiency experiments, e.g., depriving the
appendage of specific kinds of tissue; (2) the addition of extra tissues;