. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. PARASYNDESIS AND TELOSYNDESIS 47 achromatic band, has indeed been cited in evidence (Montgomery, 1903 ; Schellenberg, 1911). As, however, this break is frequently not in the middle of the loop (Schellenberg), it cannot be taken as the point of junction of the conjugating chromosomes, since the limbs of the diakinetic and metaphase rings, loops, etc., are equal. There can indeed be little doubt that these breaks are the transverse constrictions which develop across the contracting chromosomes in Lepidosiren and elsewhe
. Cytology, with special reference to the metazoan nucleus. Cells; Cytology. PARASYNDESIS AND TELOSYNDESIS 47 achromatic band, has indeed been cited in evidence (Montgomery, 1903 ; Schellenberg, 1911). As, however, this break is frequently not in the middle of the loop (Schellenberg), it cannot be taken as the point of junction of the conjugating chromosomes, since the limbs of the diakinetic and metaphase rings, loops, etc., are equal. There can indeed be little doubt that these breaks are the transverse constrictions which develop across the contracting chromosomes in Lepidosiren and elsewhere. It is. Fig. 19. A-C, parasyndesis in Planaria gonoccphala. (.'\fter Schlcip, Zool. Jaltrb. Anat.,igoy.) D-F, parasyndesis in Dyliscus marginalis {aitei Henderson, , igoy) ; A, D, leptotene; B, E, zygotene; C, F, diplotene stages. characteristic that these transverse constrictions are often by no means in the middle of the chromosomes (Fig. 65). This very short and incomplete summary of the arguments for and against the only two schemes of meiosis which can lay any claim to generality must suffice for the present. It is clear that parasyndesis is the hypothesis accepted in this book, and we shall find, especially in Chapters V. and VI., that we continually meet with observations as well as experimental results which are readily intelligible on the assumption that conjugation of the chromosomes takes place by parasyndesis, but are quite inexplicable on the theory of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Agar, Wilfred Eade, 1882-. London Macmillan
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