HYBRIDS BETWEEN FUNDULXJS AND MACKEREL 405 



pared with pure F. heteroclitus. A second individual was drawn 

 and shown in figure 1. This individual is nearly normal, but has 

 not grown to more than half of the size of the hatched individual. 

 The large mass of yolk still remaining is probably destined to re- 

 main undigested. This individual lived for over a week longer and 

 never hatched. The third and last individual is very much like 

 figure 1, but somewhat smaller and less advanced. All three 

 show only Fundulus chromatophores, though the black chromat- 

 ophores are somewhat branched, a condition seen however in 

 many pure-bred Fundulus larvae in stages just prior to hatching. 



Class B. All five embryos are still alive, but are decidedly 

 abnormal. The anterior parts are better developed than the 

 posterior parts. They have rather large eyes and the tail fin has 

 failed to differentiate. Although these embryos had never 

 established a circulation, they have evidently been able to assim- 

 ilate a considerable amount of yolk as is indicated by the dimin- 

 ished mass of the latter. The early observations showed no 

 distinct evidences of paternal heredity and there are still no green 

 chromatophores ; so one may consider this group as pure maternal. 



Class C. The two embryos in this class now show no circula- 

 tion. The rather weak partial circulation seen earlier has been 

 inadequate. The development is now decidedly subnormal, 

 the eyes being vaguely defined and the heads small. In both 

 embryos the green chromatophores are much more numerous 

 than when previously examined. Evidently the paternal in- 

 fluence was somewhat belated, but operated strongly to retard 

 development when once it gained momentum. Perhaps this is a 

 case of delayed dominance. 



Class D. All eight individuals are still alive, and it is in this 

 group that now occur the best cases of reduced head parts and 

 comparatively well-developed trunk. One individual has an 

 amorphous head and a fairly well-developed caudal fin. One 

 individual is cyclopic with the eye bilobed and directed toward 

 the anterior. The others have narrow heads with small indis- 

 tinct eyes. The maternal types of chromatophores are still 

 somewhat in the ascendency, but the difference is not so striking 

 as at the former census. 



