TANNING IN THE ADULT FLY: A NEW FUNCTION OF NEUROSECRETION IN THE BRAIN.

Tanning in the newly emerged fly is induced by a hormone secreted by neurosecretory cells situated in the pars intercerebralis of the brain. The same hormone is contained in the compound ganglion of the thorax, in concentrations six times as high as in the brain. This hormone is believed to act directly on the eflector organ, and not through the secretion of ecdyson or a corpus allatum hormone; its release is effected through nervous impulses reaching the brain by way of the ventral nervous system a few minutes after the fly has emerged from the puparium. The hormone appears to be different from both the prothoraco-tropic and the gonadotropic hormones.