Abstract
In a previous paper 1 experiments were described which were designed to test the developmental capacity of the pars buccalis of the amphibian pituitary body, when prevented from making contact with the infundibular region of the brain. The experiments consisted in shifting the presumptive infundibular region of the late gastrula of Hyla regilla to a position posterior to that of the normal, thus forcing it out of reach of the pars buccalis, when the latter migrates inward to assume its definitive position at the anterior end of the notochord. At the time of operation, the anlagen of the two components of the pituitary body were separated by a distance equivalent to a quarter of the length of the embryo and it may be supposed that they exerted no influence over each other. This condition, however, does not prevail in post-neurula stages.
Tadpoles derived from gastrulæ upon which the operation had been performed exhibited the silvery-white condition which results from deficiency of secretion of the pars intermedia of the pituitary body. Histological examination of the “albino” specimens revealed that the infundibular recess had formed from the floor of the myelencephalon instead of from that of the diencephalon; the pars buccalis was situated in its normal position at the anterior end of the notochord and remained as a compact, darkly staining and comparatively undifferentiated body of cells, showing no trace of pars intermedia tissue.
From data available at the time, it was not possible to determine whether or not the isolated partes buccales of these “albino” larvae represented functional anterior lobes. Subsequent work, however, has illuminated this point.
The operation mentioned above was performed upon 52 gastrulæ of Hyla regilla. Of these, 47 developed into albino larvae which were cultured in sterilized spring water, fed upon boiled egg yolk, and maintained alive until the present time.
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