| Description | Slide shows four diagrams demonstrating 'the development of regions by dependent differentiation during the stage of plasticity, before the onset of irreversible determination'.
Diagrams are labelled 'a' to 'd'.
Text below images reads: 'Fig 14 - The development of regions by dependent differentiation during the stage of plasticity, before the onset of irreversible determination. At the early gastrula stage, a piece of presumptive epidermis (gill region) of Triton Cristatus is exchanged for a piece of presumptive brain region of T. taeniatus. a, The dark taeniatus embryo with the light cristatus graft. b, The light cristatus embryo with the dark taeniatus graft. c, The teaniatus embryo at a later stage, with the cristatus graft in region of the left side of the brain. d, Transverse section through the taeniatus embryo, showing part of the wall of the forebrain (between X-X) formed from the grafted light coloured cristatus tissue, which has undergone dependent differentiation according to its surroundings. (From Spemann, Arch, Entwmech. xlviii, 1921.)' |