PHYSIOLOGICAL CHARACTERISTICS OF AXIATE PATTERNS 113 



lar fractions of body length from small, young animals usually show in- 

 crease. With decrease in relative length of piece, increase in susceptibility 

 after section becomes greater. Moreover, in pieces of equal length from 

 the anterior zooid the increase is greater with increasing distance of the 

 piece from the anterior end; susceptibility of pieces from the posterior 

 part of the anterior zooid becomes as high as, or even higher than, that of 

 anterior pieces. Pieces from the posterior zooid region resemble anterior 

 pieces in showing less increase in susceptibility than posterior pieces of 



/X 



T'. 



Ir- 



J 



\r-l^ 



B 



YT 



l-J 



H 



r'i i^ 





TT 



D G J 



Fig. 2,2,, A-J . — Differential susceptibility of Dngesia dorotocephala in KCN. A-D, m/i,ooo, 

 alkaline; E-G, ni/i,ooo, neutral or slightly acid; H-J, m/io,ooo, alkaline. Arrows indicate 

 direction of progress of disintegration. 



the anterior zooid. In general, the effect of section on these shorter pieces 

 is obliteration or, in shorter pieces, inversion of the susceptibility gradient 

 of intact animals. The posterior region of the anterior zooid becomes 

 equally susceptible to, or more susceptible than, other regions. These al- 

 terations of susceptibility are temporary and apparently represent a stim- 

 ulation of the pieces following section. They gradually disappear, the 

 gradient in pieces becoming similar to that of intact animals after 12 hours 

 or more (Child, 1914c). That they indicate real, though temporary, 

 changes in physiological condition at different body-levels, in relation to 



