172 FRANK W. BANCROFT 
Fig. 4 Pure F. heteroclitus, five days old, showing the brain chromatophores 
and half of the yolk chromatophore ring about the embryo. H=heart. 25. 
Fig. 5 Pure F. heteroclitus, six days old, showing the first crop of brain chro- 
matophores well expanded. Red brain chromatophores not drawn. % 25. 
Fig. 6 Same embryo drawn in fig. 5, but nineteen hours later showing the first 
appearance of the second crop of brain chromatophores. The four cells of the 
first crop still recognizable. 25. 
Fig. 7 Same embryo drawn in fig. 6, but forty-eight hours later. Shows the 
fusion of the head chromatophores. 
