SUMMARY

The luteinizing hormone (LH) content of the anterior pituitary of the domestic fowl has been determined at different times during the interval between successive clutches of eggs. The LH content remained constant for 12\p=n-\14 hr. after the ovulation of the last egg of the sequence, decreased 16 hr. before ovulation, rose again to a peak 12 hr. before ovulation and decreased to lower levels 4 and 8 hr. before the ovulation itself, at which point levels had risen to the normal values. These changes are discussed in relation to the lighting sequence and times of oviposition. It is suggested that the decreased levels 4\p=n-\8 hr. before ovulation represents the release of ovulatory LH