MODES OF INHERITANCE IN HYBRIDS 



463 



TABLE 4 

 Comparing hybrids from F. majalis 9 X F. diaphanus cT with pure F. majalis 



3 hours 

 6 hours 



22 hours 



2 days 



3 days 



4 days 



5 days 



1 week 



PURE F. MAJALIS (CONTROL) 



In 2- and 4-cell stages 

 16 to 32 cells 



Blastoderm beginning to form 

 faint germ ring 



Germ ring about halfway around 

 yolk, triangular embryonic 

 shield, embryonic axis a thin 

 line 



Germ ring nearly around yolk 

 but blastopore still widely 

 open, optic vesicles flat with- 

 out optic cups, no lenses, no 

 mesoblastic somites 



Embryos with many somites, 

 well differentiated brain ves- 

 icles, no heart-beat, no circu- 

 lation, no pigment 



Embryo large, heart-beat and 

 circulation well established, 

 no chromatophores 



Embryos very much larger than 

 hybrids, a few slender black 

 chromatophores on sides of 

 mid- and hind-brains, slen- 

 der black chromatophores on 

 yolk, no red yolk chromato- 

 phores 



F. MAJALIS 9 X F. DIAPHANUS cf 



Same 



Mostly 32-cell stages 



Blastoderm much broader than 

 in control, germ ring well de- 

 fined, embryonic shield begin- 

 ning to appear as a thickening 

 of germ ring 



Germ ring in more advanced em- 

 bryos as much as two-thirds 

 around yolk, embryonic axis 

 more sharply defined than in 

 control 



Blastopore closed, optic cups 

 formed, lens flat, 4 to 7 somites 



Embryos smaller but more ad- 

 vanced than control, no heart- 

 beat or circulation, scattering 

 slender black chromatophores 

 on yolk, none on body 



Embryos about as advanced as 

 control in general develop- 

 ment, but much smaller in size, 

 all show the paternal influence 

 in pigmentation, since there 

 are both black and red chro- 

 matophores on yolk and black 

 chromatophores of the F. dia- 

 phanus type, or nearly so, on 

 the sides of the hind-brain 



Hybrids much smaller, eyes paler, 

 head chromatophores almost 

 pure paternal in type, black 

 yolk chromatophores almost 

 pure paternal, red yolk chroma- 

 tophores intermediate in form 

 and color between two parental 

 types. Red chromatophores in 

 three rows on side of body as 

 in F. diaphanus 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 16, NO. 4 



