Improved surface visualization of living avian blastoderm structures and neighbouring ooplasms by oocytal trypan-blue staining

By injection(s) of trypan-blue solution during late oogenesis (rapid growth period of the oocytes) into the mother quail we could improve the visibility of the structural details seen from the surface in living quail blastoderms when still in situ on their egg yolk balls. This technique of intraoocytal yolk staining by trypan blue allows us to observe, to focus on and to photograph much better the surface morphology of unincubated or shortly incubated blastoderms and their relationship with the neighbouring ooplasms. Indeed the difference in distribution and volume of the trypan-blue-stained yolk granules in the blastoderms and neighbouring ooplasms seems to prevent excessive reflexion by the deep part of the germ disc of the light penetrating through the superficial parts. This diminished scattering of light, greatly increases the contrast between the different regions. By this method we could visualize a higher number of RAUBER's sickles from the surface in living unincubated quail blastoderms.