Abstract
Some years ago the writer demonstrated 1 that implantation of the combined pars intermedia and pars nervosa of adult frogs into tadpoles causes heavy pigmentation and transitory contraction of the body walls lasting several days. In a later paper 2 it was shown by transplantation of each part separated from the other, that the pars intermedia is alone involved in inducing pigmentation. The contraction of the body walls is conspicuous enough but difficult to measure. The object of the present paper is to present the results of such an evaluation. This was accomplished by measuring the area of the shadow cast by vertical illumination of each tadpole upon photographic print paper. Each print was projected upon paper by an opaque projection lantern and magnified 5 diameters. The area of each image was then measured with a planimeter, several such measurements of each tadpole used in the experiment being made at different times.
Transplants of pars anterior, pars intermedia, and pars nervosa were placed in a pocket under the skin over the right eye of Rana aurora tadpoles. This makes possible the location and later examination of the transplant in each case. The methods followed, though very labrious, do not give a quantitative measure of results but they do give a decision as to the effects of these implants upon body contour. It is felt that such painstaking studies upon a few specimens are more valuable than less careful studies of many. This method is considered preferable to volumetric methods because of the difficulty of separating water from the tadpoles without injury to them. Anaesthetization with ether in water may have slightly retarded growth during the period of the experiment, but the methods were impartially applied and it is felt that they serve as a fair index of the situation.
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