STUDIES ON THE DYNAMICS OF MORPHOGENESIS 



295 



and joins the curve af as indicated by the dotted line drawn from 

 X in fig. 40. In other words the first sixteenth piece forms a 

 large percentage of tailless heads instead of wholes. 



It is also evident from this figure that the region in which 

 headless tails occur is not a definite morphological region of the 

 body, for we see that its extent increases with decreasing size of 

 the pieces. The various curves turned upside down would 

 represent the frequency of headless tails. 



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Fig. 41 Graphic representation of the percentages of "normal eyes" in pieces 

 of different size and from different regions. The data for the curves are from 

 table I and the method of construction is the same as in fig. 40. The curve xb 

 shows the normal eyes at the different levels of section in the quarter pieces: the 

 curve yc, in the sixth pieces: the curve ad, in the eighth pieces: the curve ae, in 

 the twelfth pieces, and the curve af, in the sixteenth pieces. Each of these 

 curves can be compared directly with the corresponding curve of fig. 40. 



In the sixteenth pieces the regions of whole formation are most 

 narrowly limited: at the extreme anterior end of the body only 

 30 per cent of wholes occur, as indicated by the beginning of the 

 curve at x all other pieces giving rise to tailless heads; then the 

 frequency rises to 90 per cent in the second sixteenth but falls 

 again to zero in the fifth and attains 100 per cent only in the six- 

 teenth sixteenth. 



