BLASTOGENESIS AND MORPHOGENESIS
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that the mode of organogenesis is not fundamental in the construction of
specific organization; it is a function of the nature of the germinal components. Starting from different germinal structures, egg or bud, by very
dissimilar organogenic processes, the embryogenic and blastogenic developments form organisms, zoologically and specifically identical.
IX. Blastogenesis and Epigenetic Evolution
Before reaching its objective, the specific animal, the egg can form,
along the way, adaptive temporary larval structures which metamorphosis corrects and eliminates; or rather, it produces primordia of
ancestral embryonic stages which disappear as the definitive organization is created.
The bud is never charged with similar complications. It goes straight
to the end without any ontogenic map. It is freed from the obligations
which the phylogenetic past imposes on embryology. The egg, by contrast,
keeps the imprint of it; it is the depository for it. At each stage of evolution its heritage, while maintaining the essential acquisitions, adds others;
its genome is modified, is enriched by such new genes that embryonic
development, repeating hurriedly and partially what it was capable of
in the most primitive forms, goes beyond these ancestral structures of
the past, which are now only provisionally outlined, and new structures
are substituted for their definitively.
Thus, it is in the egg that evolution is inscribed, and it is by means
of it that evolution acts. These obvious facts, which the comparison
between ontogenesis and blastogenesis brings to light so clearly, must be
kept in mind if we wish our concepts of evolution not to remain frozen
in their impotency and to emerge from the rut where they have been
immobilized for more than 50 years. Evolution in the true sense of the
word cannot be confused with "speciation." It cannot be resolved by
molecular and genetic abstraction. Evolution is a transformation, thus
an organogenic creation. It cannot be accomplished by chance, or in any
way, and be the sole result of natural selection. Evolution is epigenetic
(P. Brien, 1967).
Blastogenic animals provide much information on this subject. Bryozoans and tunicates, sedentary and budding, are derived from groups
initially free; their attachment to a support takes away all their mobility
and reduces them in organization. However, these animals do not die.
The strange mutation which strikes them would have been able to imperil
their existence if it had not been corrected at the same time, rectified by
correlative organogenic transformations by which these animals finally
199
that the mode of organogenesis is not fundamental in the construction of
specific organization; it is a function of the nature of the germinal components. Starting from different germinal structures, egg or bud, by very
dissimilar organogenic processes, the embryogenic and blastogenic developments form organisms, zoologically and specifically identical.
IX. Blastogenesis and Epigenetic Evolution
Before reaching its objective, the specific animal, the egg can form,
along the way, adaptive temporary larval structures which metamorphosis corrects and eliminates; or rather, it produces primordia of
ancestral embryonic stages which disappear as the definitive organization is created.
The bud is never charged with similar complications. It goes straight
to the end without any ontogenic map. It is freed from the obligations
which the phylogenetic past imposes on embryology. The egg, by contrast,
keeps the imprint of it; it is the depository for it. At each stage of evolution its heritage, while maintaining the essential acquisitions, adds others;
its genome is modified, is enriched by such new genes that embryonic
development, repeating hurriedly and partially what it was capable of
in the most primitive forms, goes beyond these ancestral structures of
the past, which are now only provisionally outlined, and new structures
are substituted for their definitively.
Thus, it is in the egg that evolution is inscribed, and it is by means
of it that evolution acts. These obvious facts, which the comparison
between ontogenesis and blastogenesis brings to light so clearly, must be
kept in mind if we wish our concepts of evolution not to remain frozen
in their impotency and to emerge from the rut where they have been
immobilized for more than 50 years. Evolution in the true sense of the
word cannot be confused with "speciation." It cannot be resolved by
molecular and genetic abstraction. Evolution is a transformation, thus
an organogenic creation. It cannot be accomplished by chance, or in any
way, and be the sole result of natural selection. Evolution is epigenetic
(P. Brien, 1967).
Blastogenic animals provide much information on this subject. Bryozoans and tunicates, sedentary and budding, are derived from groups
initially free; their attachment to a support takes away all their mobility
and reduces them in organization. However, these animals do not die.
The strange mutation which strikes them would have been able to imperil
their existence if it had not been corrected at the same time, rectified by
correlative organogenic transformations by which these animals finally