No. I.] 



THE ECHINODERM EGG. 



329 



.\A\hJ. 



\M.i 



%|l|p '^f/ljlff 



c 



Fig. 3. Fusion of the pronuclei, fission of the arch opl asm-mass, and formation 

 of the cleavage-amphiaster in Toxopneustes. A, " aureole-phase " {cf. Fol, Fig. 4) ; 

 B, double-aster (cf. Fol, Fig. 5); C pause (cf. Fol, Fig. 8); D, early cleavage- 

 amphiaster (cf. Fol, Figs. 9 and loV 



