. Senescence and rejuvenescence. Age; Reproduction. 112 SENESCENCE AND REJUVENESCENCE Anophthalmic.—The anterior outgrowth of new tissue is vari- able in form and without eyes, but contains a small, single, gangli- onic mass, , it is a rudimentary head (Figs. 22 A, 22 B). Headless.—The anterior outgrowth merely fills in the contracted cut surface and does not extend beyond the contours of the margin; the posterior outgrowth, however, is usually even longer than in other pieces, but its differentiation proceeds very slowly and is never completed as long as it is attached to the headless pie
. Senescence and rejuvenescence. Age; Reproduction. 112 SENESCENCE AND REJUVENESCENCE Anophthalmic.—The anterior outgrowth of new tissue is vari- able in form and without eyes, but contains a small, single, gangli- onic mass, , it is a rudimentary head (Figs. 22 A, 22 B). Headless.—The anterior outgrowth merely fills in the contracted cut surface and does not extend beyond the contours of the margin; the posterior outgrowth, however, is usually even longer than in other pieces, but its differentiation proceeds very slowly and is never completed as long as it is attached to the headless piece (Fig- 23). The difference between the extremes of this series, the normal and headless forms, in the degree of reorganization is very great,. Figs. 21-23.^—-DifEerent degrees of reconstitutipn in Planaria dorotocephala: Fig. 21 A, B, teratomorphic forms; Fig. 22 A, B, anophthalmic forms; Fig. 23, headless form. particularly in pieces from the postoral region (eg., a, Fig. 24). In the development of a normal animal the anterior half or more of such a piece undergoes extensive changes in giving rise to a phar)ai- geal and prepharyngeal region, and outgrowths of new tissue appear at both ends. In the piece from this region which remains headless no prepharyngeal or pharyngeal region arises, and changes are limited to the longer outgrowth at the posterior end and the smaller amount of new tissue at the anterior end. In the teratophthalmic, teratomorphic, and anophthalmic forms the degree of reconstitutional change ranges from a little less than in the normal animal to somewhat more than in the headless form. Moreover the degree of reconstitution decreases somewhat as the. 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 Child, Charles Manning, 1869-1954. Chicago, Ill. , The University of Chicago Press
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectreproduction, bookyea
