Abstract
1. In the pupal stage of the cecropia silkworm, antigen 7, a protein with the solubility characteristics of an albumin, is present in female blood in approximately a thousand times higher concentration than in the blood of males. Antigen 7 is undetectable in the blood of larvae of either sex. It first appears in the blood after the larva has spun its cocoon, and is present throughout all subsequent stages of metamorphosis. Late in the pupal-adult transformation, when the eggs are produced, the concentration of antigen 7 in female blood decreases significantly.