DYNAMICS OF MORPHOGENESIS 



131 



The table shows very great differences in the character and fre- 

 quency of head-formation at the different temperatures, but the 

 evidences for the existence of an axial gradient appear only on 

 examination of the individual pieces. At the higher temperature 

 74 per cent of the pieces were like figure 43, with large head, well 

 developed pharynx and long, pointed posterior outgrowth. The 

 alimentary tract (not shown in the figure) is well developed in the 

 new posterior end. Figures 44 and 45 represent the two extremes 

 after thirty-six days at the lower temperature. Only 26 per cent 

 of the pieces were like figure 44, the others being intermediate 

 between it and figure 45, or like the latter. In all of these pieces 



44 



45 



Figs. 43 to 45 Regulation at different temperatures: pieces include region 

 between levels 2 and 3 in figure 32. Figure 43, regulation at high temperature. 

 Figures 44 and 45, regulation low temperature. 



at low temperature the outgrowth at the posterior end of the 

 pi^ce is almost entirely inhibited. Even in figure 44, which 

 represents the most complete regulation at the lower temperature, 

 the new tissue merely fills the contracted wound and shows no 

 actual outgrowth beyond the contour of adjoining parts. There 

 is no trace of posterior intestinal regulation but a normal though 

 small pharynx and a normal head' have developed. Evidently 

 the low temperature inhibits posterior regulation to a very large 

 extent, but 68 per cent of the pieces in which posterior regulation 

 was like that in figures 44 and 45 developed heads of some kind 

 and 26 per cent developed normal heads. In the extreme headless 



