HYBRID VIGOR IN DROSOPHILA 



475 



races than Inbred 92 or Homozygous. Correlation exists between the egg pro- 

 duction of the race and its fitness to survive as judged by its duration of life 

 as measured by the survival of either males or females. 



The hybrid race came from the cross Inbred 92 and Ames I. The mean 

 productions of the parents were 389 and 1000 eggs respectively over the life- 



FiG. 29.1 — Photograph of laying cap with eggs and some hatched larvae. 



time period. The mean production of the hybrid was 2034 eggs, or 203 per 

 cent greater than that of its high producing parent, Ames I, and 422 per cent 

 greater than that of its other parent. Inbred 92. The hybrid showed more 

 eggs than any of the pure races. The excess of the hybrid over the pure par- 

 ents is greater in this particular experiment than in several other similar ex- 

 periments. 



The females of the different races showed average egg laying periods of 

 17.2 to 46.0 days. The hybrid lays eggs nearly as long as the higher producing 



