56 INDIVIDUALITY IN ORGANISMS 



In cyanide the body undergoes some contraction, 

 death begins at the apical end (Fig. 4) and is accom- 

 panied by the instantaneous loss of all movement and 

 disintegration of structure in the part concerned, and the 

 protoplasm swells and spreads out in the water, as indi- 

 cated by the dotted outline in Fig. 4. Other parts 

 remain intact and the cilia continue to vibrate. From 

 the apical region death and disintegration proceed along 

 the body as shown in Figs. 5-7, the line of demarcation 

 between the dead and disintegrated and the living 

 portions remaining distinct at all times until the progress 

 of death ends at the basal end of the body. The rate 

 of progress of death over the whole body may vary from 

 a few seconds to five or ten minutes, according to con- 

 centration of cyanide used, temperature, and other con- 

 ditions. Deviations from this course are very rare and 

 are probably the result of local stimulations of one part 

 or another of the body. 



In Fig. 8 the beginning of death and disintegration 

 in the unfertilized starfish egg is shown. The region of 

 the egg where disintegration begins is that region where 

 the nucleus lies nearest the surface. When the egg 

 develops this region gives rise to the apical end of the 

 embryo and larva. From this region disintegration 

 proceeds through the egg along the axis determined by 

 the eccentric position of the nucleus (Fig. 9), and this 

 axis corresponds with the major axis of the embryo and 

 larva. The same susceptibility gradient also appears 

 in embryonic and early larval stages. In these cases the 

 death gradient does not indicate the presence of more 

 than one axis. In many forms other axes are also 

 indicated by the course of death. In the embryo of the 



