Abstract INTRODUCTION Attempts by this laboratory to grow chick embryos outside the shell were met with limited success (Boone, 1963). Among the environmental factors altered by the in vitro method of growing embryos was exposure to light. Boone (1969) found that average livability was 3.7 and 2.7 days in black painted and ordinary beakers respectively. That research involved three separate trials and a total of 112 embryos. Literature concerning the effect of light on the chick embryo is limited and conflicting. Shutze et al. (1962) exposed Leghorn eggs to light, and caused chicks to hatch one day earlier than controls. Hatchability of fertile eggs was not adversely affected by using lights in the incubator. The light intensity was less important than the mere presence of light. Voitle (1970) indicated that the longer the eggs were exposed to light, the faster the chicks hatched. Continuous light improved maturation of the navel as…