A PRELIMINARY EXPERIMENTAL ANALYSIS 



49 





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Fig. 1 8 



The labile determination of regions, o, Morula of Triton, showing the cells 

 subsequently isolated indicated by lines. The remaining cells were destroyed 

 with needles, their contents forming a supporting and nutritive medium sur- 

 rounding the four living cells, b, i hour after operation, the four living cells have 

 divided to form eight, c, g days after operation, the cells have produced a com- 

 plicated structure, d, Section through c; nervous tissue («.), a lens (/.), muscle 

 segments (w.) and epidermis (e.) have been differentiated. It is to be noted that 

 no organiser was present in the explanted cells and that no gastrulation took 

 place ; the differentiations are therefore the effects of labile determinations of the 

 cells themselves. (From Holtfreter, Arch. Entwrnech. cxxiv, 193 1.) 



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