DEDIFFERENTIATION IN ECHINUS LARVAE. 235 



LIST OF FIGURES. 



All figures were drawn from life with the aid of an Abbe camera lucida, 

 at table level. All are drawn with the combination of a Reichert 1/3" lens 

 and a No. 4 ocular, with the exception of Fig. 2, b (1/6" lens + 4 ocular), 

 and Fig. 10 (%" lens + 2 ocular, reduced to half-size). Figs. 6 and 10 

 have been reduced to one-half diameter, all others to two-thirds. 



