"I may finally call attention to the probability that the association of paternal and maternal chromosomes in pairs and their subsequent separation during the reducing division ... may constitute the physical basis of the Mendelian law of heredity." [emphasis added]. W Sutton (1902) Biol. Bull. 4: 24-39:

 "1. The chromosome group of the presynaptic germ-cells is made up of two equivalent chromosome-series, and that strong ground exists for the conclusion that one of these is paternal and the other maternal. [Fig.1]
    2. The process of synapsis (pseudo-reduction) consists in the union in pairs of the homologous members (i. e., those that correspond in size) of the two series. [Fig. 5a]
    3. The first post-synaptic or maturation mitosis is equational and hence results in no chromosomic differentiation. [Fig. 5b]
    4. The second post-synaptic division is a reducing division, resulting in the separation of the chromosomes which have conjugated in synapsis, and their relegation to different germ-cells [Fig. 9].
    5. The chromosomes retain a morphological individuality throughout the various cell-divisions."

W. S. Sutton (1903) The Chromosomes in Heredity Biol. Bull. 4: 231-251 [emphasis added]

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