176 FRANK W. BANCROFT 
24 23 22 
Fig. 20 Pure F. heteroclitus, seven days old. Same embryo as in fig. 18. 
Chromatophores on blood vessel near left eye. "To show increase in size and com- 
plexity during last twenty-four hours. 114. 
Fig. 21 F. heteroclitus egg hybrid. Same embryo as in fig. 19. Chromato- 
phores on blood vessel near left eye. Note increase in size of red chromatophores 
and the beginning of the small processes of black chromatophores. 114. 
Fig. 22 Pure F. heteroclitus, eleven days old. Typical fully developed red 
chromatophore among the black chromatophore reticulum.  I14. 
Fig. 23 F. heteroclitus egg hybrid, eleven days old. Of same age and series 
as embryo in fig. 22, with which it is to be compared. Note double layer of chro- 
matophores and fine black reticular processes. X 114. 
Fig. 24 Pure F. heteroclitus. Most of the eggs of this lot had hatched, but 
in this embryo the circulation had stopped though the heart was still beating, and 
the blood vessels distinct and full of blood. The yolk chromatophores have begun 
to lose their arrangement on the blood vessels and have developed much longer 
branches than any normally seen in this species. > 114. 
