The Process of Heredity 527 



had evidently ceased to develop. The largest specimens had 

 reached a size almost equal to that of the average H pure on hatch- 

 ing. The color pattern of the head and back was almost identical 

 with that of the two heteroclitus strains on hatching. The yolk 

 was very heavily pigmented and was still a large mass. The M 

 pures were on the average nearly twice as large as the M hybrids. 

 The body was pigmented with large grayish chromatophores. 

 The yolk was lightly pigmented with black. 



At 13 days: About fifty more H pures hatched. No more H 

 hybrids hatched in spite of the water being changed and the conse- 

 quent stimulus afforded by the mechanical disturbance and the 

 sudden change of temperature. M hybrids and M pures in 

 relatively the same condition as on the previous day. 



At 14 days: Practically all of the H pures hatched. Only a 

 few anaemic specimens left unhatched. No more H hybrids 

 hatched, but they had become more heavily pigmented, especially 

 on the yolk. A large specimen, with heavily pigmented yolk, 

 was dissected out of the egg membrane and it lay almost inert in 

 the sea-water, showing that it was not ready for hatching. The 

 length of this specimen was 7.5 mm., while that of the first H 

 hybrid hatched was 7.2 mm., and that of the first hatched H pure 

 was 7.3 mm. This embryo then although not nearly ready to 

 hatch, was somewhat longer than the hatched embryos of either F. 

 heteroclitus strain. Late in the evening of the same day six 

 more H hybrids hatched without artificial disturbance. M pures 

 greatly increased in size, but M hybrids no larger than at the last 

 observation. 



At 15 days: Fifteen more i^ hybrids hatched. A typical speci- 

 men of this lot was quieted and drawn (Plate V, Fig. h.) 



At 16 days: Twenty-two more H hybrids hatched. Only the 

 abnormal specimens, that could never hatch, were left within the 

 membranes. These latter number about 25 per cent of the whole. 

 The H hybrids hatched out during the day were not nearly so 

 heavily pigmented as those that hatched out earlier. They were 

 also somewhat sluggish on hatching, some of them appearing to 

 be cramped by over-long confinement within the egg membrane. 

 A considerable number of those that hatched on this day did so 



