. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 136. Experimental hemi-embryos from frog's eggs, a, an early stage; B, a tadpole with its missing half partly restored; c, cross section of b, showing two notochords. (After Walter.) The ability to perform such a recovery or to develop an organ from an extirpated embryonic bud lasts for only a critical brief period. Once this time is past, if the sequence of normal events is interrupted, the internal mechanism is unable to carry out the original struc
. Biology of the vertebrates : a comparative study of man and his animal allies. Vertebrates; Vertebrates -- Anatomy; Anatomy, Comparative. Fig. 136. Experimental hemi-embryos from frog's eggs, a, an early stage; B, a tadpole with its missing half partly restored; c, cross section of b, showing two notochords. (After Walter.) The ability to perform such a recovery or to develop an organ from an extirpated embryonic bud lasts for only a critical brief period. Once this time is past, if the sequence of normal events is interrupted, the internal mechanism is unable to carry out the original structural design. The par- ticular region of a developing organism that possesses this magical power of directing internal operations is called an organization center. One of the earliest organization centers is around the dorsal lip of the blastopore where the mesoderm is organized. This primary center is suc- ceeded by other formative centers, secondary, tertiary, and so on, each of which is dependent upon the successful operation of preceding centers. The discovery of such formative centers by Spemann, Harrison, and others through experiments upon developing embryos, is a promising beginning towards solving the problem of why the architectural plan of a particular species is carried out successfully in the innumerable individuals which grow to 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 Walter, Herbert Eugene, b. 1867; Sayles, Leonard Perkins, 1902-. New York : Macmillan Co.
Size: 1544px × 1619px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksubjectanatomycomparative, booksubjectverte
