268
CHARLES Ε.
WILDE
with a very high probability, pigment cells originate solely from the
neural crest (neuro-epithelium) in all classes and orders of vertebrates.
The neural crest (ganglionleiste) consists of a ridge of cells bounding
the medullary plate in early vertebrate embryos. It is classically seen at
the stage of the neurula. The neural crest probably blends gradually in
terms of its differentiative potency into the interior of the medullary
plate while its lateral edges are discretely bounded by the edge of the
morphological 'ridge' demarking the crest from the adjacent presumptive epidermis. In the head region of most vertebrate embryos, however,
there are probably certain Outlyers' or epidermal placodes which exhibit
neural crest-like potency (see below) but which probably do not contribute pigmented cells to the body; rather they appear to be concerned
with sensory nerve ganglia and ectomesenchyme production, two other
discrete units of cell type derived from the same embryonic area
(Bartelmez, 1954).
The vertebrate embryo then, produces pigmented cells from a definable
embryonic area with a finite exterior border. The interior border blends
gradually, or indeterminately into more completely neurogenic areas.
It is therefore preferable to write, with regard to pigment cell production, of a 'neuro-epithelium' the lateral borders of which are concerned
with quantity production of pigment cells although there is some
contribution from other areas of the neuro-epithelium (Niu, 1947;
Hörstadius, 1950).
Early pigment cells, promelanoblasts or melanoblasts are endowed
with wide migratory powers and colonize many areas of the body. In
most cases the migration takes place prior to the onset of the major
portions of the process of pigment production. Migration slows or
ceases at this time, but whether a total cessation of migration occurs in
all vertebrates must be considered an open question.
The abundance of work on vertebrate pigment cells and the interest
of students of medicine in the acute problems of pigmented cell neoplasms has led in the past years to the establishment of a group of
investigators, informally associated, who have gathered together every
two years to exchange information and to review progress in the field of
the biology of pigmented cells. This group, under the leadership of the
late Myron Gordon, has published the results of its meetings in a series
of volumes (Gordon, 1948, 1950, 1953, 1959), which serve as a central
compendium for review of much of the current information in the field.
The present review would indeed be redundant in the face of the
publication of the most recent volume by this group if a broad survey
of the field were to be made. The present author therefore will make no
attempt at completeness in coverage but will attempt to contribute an
analytical and occasionally speculative interpretation of current and
CHARLES Ε.
WILDE
with a very high probability, pigment cells originate solely from the
neural crest (neuro-epithelium) in all classes and orders of vertebrates.
The neural crest (ganglionleiste) consists of a ridge of cells bounding
the medullary plate in early vertebrate embryos. It is classically seen at
the stage of the neurula. The neural crest probably blends gradually in
terms of its differentiative potency into the interior of the medullary
plate while its lateral edges are discretely bounded by the edge of the
morphological 'ridge' demarking the crest from the adjacent presumptive epidermis. In the head region of most vertebrate embryos, however,
there are probably certain Outlyers' or epidermal placodes which exhibit
neural crest-like potency (see below) but which probably do not contribute pigmented cells to the body; rather they appear to be concerned
with sensory nerve ganglia and ectomesenchyme production, two other
discrete units of cell type derived from the same embryonic area
(Bartelmez, 1954).
The vertebrate embryo then, produces pigmented cells from a definable
embryonic area with a finite exterior border. The interior border blends
gradually, or indeterminately into more completely neurogenic areas.
It is therefore preferable to write, with regard to pigment cell production, of a 'neuro-epithelium' the lateral borders of which are concerned
with quantity production of pigment cells although there is some
contribution from other areas of the neuro-epithelium (Niu, 1947;
Hörstadius, 1950).
Early pigment cells, promelanoblasts or melanoblasts are endowed
with wide migratory powers and colonize many areas of the body. In
most cases the migration takes place prior to the onset of the major
portions of the process of pigment production. Migration slows or
ceases at this time, but whether a total cessation of migration occurs in
all vertebrates must be considered an open question.
The abundance of work on vertebrate pigment cells and the interest
of students of medicine in the acute problems of pigmented cell neoplasms has led in the past years to the establishment of a group of
investigators, informally associated, who have gathered together every
two years to exchange information and to review progress in the field of
the biology of pigmented cells. This group, under the leadership of the
late Myron Gordon, has published the results of its meetings in a series
of volumes (Gordon, 1948, 1950, 1953, 1959), which serve as a central
compendium for review of much of the current information in the field.
The present review would indeed be redundant in the face of the
publication of the most recent volume by this group if a broad survey
of the field were to be made. The present author therefore will make no
attempt at completeness in coverage but will attempt to contribute an
analytical and occasionally speculative interpretation of current and