. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . the carry-ing on of ingeniously planned and carefully controlled series of experiments with re-generating animals, weare acquiring a greatmass of important data,and the interpretationand generalization ofthese data is certain tobe accomplished in thenear future. We have space hereto call attention to butone of the wavs in which V an understanding of thephenomena of regener-ation will throw light on FIG. 171. —Regeneration of the eye of Triton: one of flie
. Evolution and animal life; an elementary discussion of facts, processes, laws and theories relating to the life and evolution of animals . the carry-ing on of ingeniously planned and carefully controlled series of experiments with re-generating animals, weare acquiring a greatmass of important data,and the interpretationand generalization ofthese data is certain tobe accomplished in thenear future. We have space hereto call attention to butone of the wavs in which V an understanding of thephenomena of regener-ation will throw light on FIG. 171. —Regeneration of the eye of Triton: one of flie fundamentalA, Edge of iris with beginning lens ; B, C, D, i -, later stages of same ; E. whole eye wi th regener- problemsindevelop- atinglens. (After Wolff and Fischel ) ment. To those biolo- FIG. 170.—Regeneration of theflatworm, Planaria:A, Specimen cut in two as far forward as eyes,regenerating two half-heads ; B, cut in two atone side of middle line, smaller piece having re-generated a head ; C, cut partly in two, havingregenerated two heads in angle; D, anotherthat produced only a single head in the angle.(After Morgan.) A. 2SS EVOLUTION AND ANIMAL LIFE gists who believe with Weismann that there is a sharp distinc-tion between the germ plasm and the somatic or body plasm,and that this germ plasm is limited to the germ cells andgerm-cell producing tracts, the regeneration of a nearly wholebody or even a considerable part of a body from a region whichdoes not include a germ cell presents a serious obstacle. But before this obstaclecan be considered asone rendering thegerm plasm theoryabsolutely untenable,it is necessary toprove what the re-generated parts arecomposed of. Arethey composed sim-ply of repeated simi-lar cells, all of onetissue type, or dothey include otherkinds of cells or tis-sues than those par-ticular kinds fromwhich the regener-ated part springs?It is, of course, ad-mitted that many,indeed most cells ofthe body, can repro-duce other cells like themselv
Size: 1578px × 1584px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorkelloggvernonlvernonl, bookcentury1900, bookdecade1900
