82 



CYTOKINESIS. 



Fir. XIX. 



Fig. XX 



Fig. XXI. 



'"Vy^^-^' X-^^^cxV^ 



Fig. XXII. Fig. XXIII. 



Figs. XIX-XXIII.— Successive stages in the third cleavage of Crepidida, showing the spreading of the old sphere suhstance, the lobing 

 of the cytoplasm and the separation of the first quartette of micromeres. 



