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  1. Type-Concept, Higher Classification and Evolution.L. Hammen - 1981 - Acta Biotheoretica 30 (1).
    A study is made of the history of the type and related concepts, from Greek Antiquity up to the present. It is demonstrated that the type-concept of eighteenth century biology was based on Leibniz's concept of substantial form, and was not related to a Platonic Idea, whilst it is now generally understood in the sense of model or norm. In the present paper, a type-concept is developed which includes ontogenetic and phylogenetic time and various evolutionary mechanisms. This type (an archetype) (...)
     
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  2. Unfoldment and Manifestation: The Natural Philosphy of Evolution.L. Hammen - 1983 - Acta Biotheoretica 32 (3).
    A study is made of the general principles and theories pertaining to evolution, among which the definition, the evidences, the philosophical roots (the origin of life, the scale of nature, the morphogenetic potentialities), the three models (the Lamarckian, the Darwinistic and an alterative), and a further development of the last-mentioned model.
     
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  3. Evolution — Kritisch Gesehen.L. Hammen - 1984 - Acta Biotheoretica 33 (2).
  4. On Some Aspects of Parallel Evolution in Chelicerata.L. Hammen - 1986 - Acta Biotheoretica 35 (1-2).
    A study is made of some aspects of parallel evolution in Chelicerata. Definitions are given of parallel evolution, convergence, homology and analogy. It is pointed out that the concept of parallel evolution (parallelism) is initially formed in an empirical way, and that a judgment must be based on formal criteria. Particular attention is paid to the rôle of gene regulation in parallel evolution, to the special case of convergence as a result of heterologous regulatory mechanisms, to parallel evolution in homonomous (...)
     
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  5. The Evolution of the Chelicerate Life Cycle.L. Hammen - 1978 - Acta Biotheoretica 27 (1-2).
    A comparative study is made of the life-cyle in Chelicerata, and its evolution. Various types of forms or instars, and various evolutionary phenomena are distinguished. They are arranged in a chronological diagram constituting a general model of the evolution of the chelicerate life-cycle. A glossary is added in which terminology is defined.
     
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