BLASTOGENESIS AND MORPHOGENESIS
201
Everyone knows the astonishing expansion of the tunicates populating all
our seas. Their transformations have supported the essential role of the
pharyngobranchial wall, the modifications of which characterize the
tunicates. This process is general in the animal kingdom.
Could one reasonably think that genetic mutations, occurring by
chance, which would have had to be ordinary and appear from generation
to generation, always filtered and chosen by natural selection, would have
been able to maintain life, for all this time, of animals mortally impaired
in their organization? It is not little by little, from generation to generation, that such embryonic transformations are produced and result in
functional structures. It is in one stroke that these organs are made,
rebuilt, become complex, and are transformed, without ceasing to be
interdependent. Evolution is epigenenetic; it is achieved in embryonic
ontogenesis. Since a mutation might come to modify its changes, the
developing embryo does not remain passive. Within the limits of its selfregulation, it takes new ways; its primordia are transformed but remain
joined together in a new organic combination, the structures of which
are necessarily and sufficiently coapted to be functional.
X. Conclusions
Everything is unified. There cannot be two biologies. Asexual reproduction appears to be an experiment of nature which demonstrates
certain fundamental problems of the "condition of living" from a different angle from that which is habitually seen in sexual reproduction.
Without doubt, in the present state of our knowledge, agamic asexual
reproduction hardly provides solutions to these problems. It does invite
a comparison of the modes of their manifestation in embryogenesis and
blastogenesis to the end of discovering, beneath the secondary epiphenomena which are their own, that which is common and fundamental
to them both: creative self-regulation of structures and forms in the
living being.
General References
Abeloos, M. (1952). "La Regeneration et les Problemes de la Morphogenese."
Gauthier-Villars, Paris.
Berril, N. S. (1950). "The Tunicata." Roy. Soc, London.
Bounoure, L. (1940). "Continuity germinate et reproduction agame." GauthierVillars, Paris.
Brien, P. (1948). Morphologie et Reproduction des Tuniciers. In "Traite de Zoologie"
(P. P. Grasse, ed.), Vol. XL Masson, Paris.
Brien, P. (1959). Les Endoproctes ou Kamptozoaires. In "Traite de Zoologie" (P. P.
Grasse, ed.), Vol. V, Part 1. Masson, Paris.
201
Everyone knows the astonishing expansion of the tunicates populating all
our seas. Their transformations have supported the essential role of the
pharyngobranchial wall, the modifications of which characterize the
tunicates. This process is general in the animal kingdom.
Could one reasonably think that genetic mutations, occurring by
chance, which would have had to be ordinary and appear from generation
to generation, always filtered and chosen by natural selection, would have
been able to maintain life, for all this time, of animals mortally impaired
in their organization? It is not little by little, from generation to generation, that such embryonic transformations are produced and result in
functional structures. It is in one stroke that these organs are made,
rebuilt, become complex, and are transformed, without ceasing to be
interdependent. Evolution is epigenenetic; it is achieved in embryonic
ontogenesis. Since a mutation might come to modify its changes, the
developing embryo does not remain passive. Within the limits of its selfregulation, it takes new ways; its primordia are transformed but remain
joined together in a new organic combination, the structures of which
are necessarily and sufficiently coapted to be functional.
X. Conclusions
Everything is unified. There cannot be two biologies. Asexual reproduction appears to be an experiment of nature which demonstrates
certain fundamental problems of the "condition of living" from a different angle from that which is habitually seen in sexual reproduction.
Without doubt, in the present state of our knowledge, agamic asexual
reproduction hardly provides solutions to these problems. It does invite
a comparison of the modes of their manifestation in embryogenesis and
blastogenesis to the end of discovering, beneath the secondary epiphenomena which are their own, that which is common and fundamental
to them both: creative self-regulation of structures and forms in the
living being.
General References
Abeloos, M. (1952). "La Regeneration et les Problemes de la Morphogenese."
Gauthier-Villars, Paris.
Berril, N. S. (1950). "The Tunicata." Roy. Soc, London.
Bounoure, L. (1940). "Continuity germinate et reproduction agame." GauthierVillars, Paris.
Brien, P. (1948). Morphologie et Reproduction des Tuniciers. In "Traite de Zoologie"
(P. P. Grasse, ed.), Vol. XL Masson, Paris.
Brien, P. (1959). Les Endoproctes ou Kamptozoaires. In "Traite de Zoologie" (P. P.
Grasse, ed.), Vol. V, Part 1. Masson, Paris.