The effect of breederʼs strain (Hy-line Brown and Hy-line White W36) flock aged (28, 36, 46, 55, 66 weeks of age) and breeding season on some physiological measurements in egg, demand organs, dead supply organs and lymphoid organs were examined. At each age, 10 unhatched eggs from each genotype were examined on embryo weight percentage, Chorioallotoic  weight %, albumen pH %, yolk pH %, residual yolk %, pectoral  muscles weight %, hatch muscles weight %, heart, liver, lunges, spleen, burse weight percentage. There was a significant difference between layer breeder genotypes for lunges weight percentage the brown was higher (0.84) than the white (0.62). The breeding season had a significant effect on heart, liver, lunges weight percentages in winter higher than summer but yolk pH and residual yolk the summer higher than the winter. Breeder's age significant effect on embryo weight percentage, Chorioallotoic weight %, albumen pH %, yolk pH%, residual yolk %, hatch muscles weight % heart, liver, lunges and burse weight percentage.  It could be observed that the genetic differences among layer breeder strain and age of breeders can affect the hatchery performance. Additionally, handling of hatching eggs and incubation management can play a major role to overcome numerous hatching problems. In turn, increasing the production of table eggs and achieves the balance between supply and demand of that strategic commodity in Egyptian market.