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physiological unitsphysiologische Einheiten (ger.)

  • Protoplasmic particles that are considered basic elements of heredity.

    though cells are so generally the ultimate visible components of organisms, that they may with some show of reason be called the morphological units; yet, as they are not universal, we cannot say that this tendency to aggregate into specified forms dwells in them. Finding that in many cases a fibrous tissue arises out of a structureless blastema, without cell-formation; and finding that there are creatures, such as Rhizopods, which are not cellular, but nevertheless exhibit vital activities, and perpetuate in their progeny certain specific distinctions; we are forbidden to ascribe to cells this peculiar power of arrangement. Nor, indeed, were cells universal, would such an hypothesis be acceptable; since the formation of a cell is, to some extent a manifestation of this same peculiar power. If, then, this organic polarity can be possessed neither by the chemical units nor the morphological units, we must conceive it as possessed by certain intermediate units, which we may term, physiological. There seems no alternative but to suppose, that the chemical units combine into units immensely more complex than themselves, complex as they are; and that in each organism, the physiological units produced by this further compounding of highly compound atoms, have a more or less distinctive character. We must conclude that in each case, some slight difference of composition in these units, leading to some slight difierence in their mutual play of forces, produces a difierence in the form which the aggregate of them assumes. […] We must conclude that the likeness of any organism to either parent, is conveyed by the special tendencies of the physiological units derived from that parent. In the fertilized germ we have two groups of physiological units, slightly different in their structures […] if the assumption of a special arrangement of parts by an organism, is due to the proclivity of its physiological units towards that arrangement ; then the assumption of an arrangement of parts slightly different from that of the species, implies physiological units slightly unlike those of the species; and these slightly-unlike physiological units, communicated through the medium of sperm-cell or germ-cell, will tend, in the offspring, to build themselves into a structure similarly diverging from the average of the species.

    Spencer, H. (1864). The Principles of Biology, vol. 1: 183; 254-5.