MODES OF INHERITANCE IN HYBRIDS 



461 



TABLE 2 



Cuniporing the hybrids from F. heteroditus 9 X F. diaphnnus cf 'ivllh pure bred 



F. he'.eroclitus 



2 hours 

 4 hours 



20 hours 



52 hours 



3 days 



4 days 



5 days 



1 week 



13 (laj's 



14 days 



3 weeks 



PURE F. HETBROCLITUS (CONTROL) 



First cleavage 



32 to 64-cell stages 



Advanced cleavage but no germ 

 ring visible 



Blastopore closed or nearly so 

 in all embryos, pale chroma- 

 tophores appearing under 

 hind-brain, a few red yolk 

 chromatophores on yolk near 

 head, no black yolk chroma- 

 tophores 



Heart beginning to beat feebly 

 in nearly all embryos, no vi- 

 telline circulation. A few 

 black yolk chromatophores, 

 and fewer head chromato- 

 phores 



Vitelline and body circulation 

 established and all types of 

 chromatophores abundant 



Embryos nearly as advanced as 

 those of F. diaphanus at 6 

 days 



Body shorter and stouter than 

 in hybrid, otherwise little dif- 

 ferent exce]it in details of pig- 

 mentation 



A few hatched 



All hatched 



Larvae vigorous 



F. HETBROCLITUS 9 X F. DIAPHANUS cf 



Same 



Like control except that a small 

 percentage of eggs are less ad- 

 vanced than any of the pure 

 bred eggs, having 16 cells or less 



Some embryos show the early 

 steps in germ ring formation, 

 others are less advanced than 

 any of the control 



The normally developing embry- 

 os noticeably more advanced 

 and more deeply pigmented 

 than controls, F. diaphanus 

 type of head chromatophores 

 appearing on sides of mid- 

 brain, a few black yolk chroma- 

 tophores 



Heart beating quite strongly in 

 a few embryos, the majority 

 about as in control, a consid- 

 erable percentage of abnormal, 

 retarded embryos derived from 

 the eggs that showed lagging 

 cleavage at 4 hours 



Almost identical with control in 

 stage of development except 

 the abnormal specimens, which 

 from here on will be ignored as 

 they never hatch; the normal 

 embryos more heavily pig- 

 mented than control 



Very much like control; pigment 



- characters given in detail later 



Body rather more slender than 

 control, a few more deeply pig- 

 mented than any of the con- 

 trols 



The majority hatched 



All hatched except abnormal 

 specimens 



Larvae indistinguishable from 

 control except in details of ig- 

 mentation 



