On the development of chicken adenohypophyseal melanophore-expanding activity

Melanophore-expanding activity (MEA) was detectable at least by stage 30 of Hamburger and Hamilton (6–6.5 incubation days) in 53 whole adenohypophyseal anlagen (plus mesenchyme) from domesticated Gallus gallus embryos. This was estimated from responses to adenohypophyseal implants next to dermal melanophores of intact Rana temporaria tadpoles, as compared with control implants of embryonic myelencephalic tissue. Analyses of 27 implants of adenohypophyseal cephalic- or caudal-region tissue alone indicated that MEA was associated mostly with cephalic regions. This association started at least by stage 35 (8–9 incubation days) and continued until the 1st day post hatching, as compared with control implants of embryonic eyelid tissue.