PLATE 4 



EXPLANATION OF FIGURES 



21 to 29 Show the various types of black head chromatophores found in young 

 larvae, at hatching or at a period equivalent to this in non-hatching embryos. 

 All camera drawings under same magnification X 100). 



21 The isolated stellate type of F. diaphanus. 



22 The polygonal, unbranched, fusing type of F. heteroclitus. 



23 The radiate type with tooth-like branches on the rays, characteristic of 

 the hatched larvae of F. majalis. 



24 A typical group of head chromatophores in the hybrid larva from egg of 

 F. diaphanus and sperm of F. heteroclitus. Note the mosaic of isolated, stellate 

 F. diaphanus cells and the fused groups of polygonal F. heteroclitus cells. 



25 A typical group of head chromatophores of the reciprocal hybrid larva, 

 from F. heteroclitus egg and F. diaphanus sperm. Here we find only the stellate 

 cells of F. diaphanus, but they show the F. heteroclitus character of fusion. 



26 A typical group of head chromatophores from the hybrid larva from F. 

 majalis egg and F. diaphanus sperm. The paternal type is almost entirely 

 dominant. 



27 A typical group of head chromatophores from the reciprocal hybrid from 

 F. diaphanus egg and F. majalis sperm. The cells are intermediate in size and 

 form between those of the parent species. 



28 A typical group of head chromatophores in hybrid larva from F. hetero- 

 clitus egg and F. majalis sperm. The F. heteroclitus polygonal fused type pre- 

 dominate, but in certain regions a modified F. majalis type of cell is fairly 

 abundant. 



29 Group of head chromatophores in hybrid from F. majalis egg and F. hetero- 

 clitus sperm, showing dominance of the paternal type. 



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