. Cephalopoda. Cephalopoda. c) The ontogenetic evidence is demonstrated in the individual develop- ment of organisms. Since F. Muller and E. Haeckel, this process has been considered as a shortened recapitulation of phylogenesis. Idealistic morphology proved that the ontogenetic stages correspond to the systematic stages, more exactly'to the homologous stages of the preceding systematic stages (p. 11). Translation of these systematic stages into phylogenetic stages requires a new formulation of these ontogenetic-phylogenetic relation- ships, as done by Haeckel rather more suggestively than pre
. Cephalopoda. Cephalopoda. c) The ontogenetic evidence is demonstrated in the individual develop- ment of organisms. Since F. Muller and E. Haeckel, this process has been considered as a shortened recapitulation of phylogenesis. Idealistic morphology proved that the ontogenetic stages correspond to the systematic stages, more exactly'to the homologous stages of the preceding systematic stages (p. 11). Translation of these systematic stages into phylogenetic stages requires a new formulation of these ontogenetic-phylogenetic relation- ships, as done by Haeckel rather more suggestively than precisely in his biogenetic law. Ontogeny is not a "repetition" of phylogeny since this (p. 28), whether symbolized as a lineage or genealogy (p. 29) or represented in its true form, is basically different from ontogeny. Ontogenesis repeats the preceding ontogenesis of the ancestors which these phenomena resemble. According to phylogeny, however, there is a gradual divergence from one ontogenesis to the next. This divergence is such that the earlier stages of the ontogenesis are increasingly more conservative than the following stages (with some reservation: see p. 19). If this is a law, the observed morphological relationships should necessarily follow. The validity of this law is evident from the general causal connec- tion throughout the development. I have attempted a more precise formula- tion of this law elsewhere (Naef, 1917, p. 57). We may therefore assume that every stage of individual development of an organic form must be more primitive than the following stage. Thus, the structure of the different parts of a developing individual repeats similar structures which occur in hoinologous stages of the ances- tors and appear in the same order as these in the lineage. This formulation describes the evidence of the so-called "biogenetic law" and expresses more adequately than this the implications of the true law outlined above. Onto- genesis must thus be c
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Keywords: ., bookcentury1900, bookcollectionbiodivers, booksubjectcephalopoda
