. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 112 MARIE M. JENKINS. 68 II 14 17 TIME IN DAYS 20 23 FIGURE 2. Growth rate curve of planarians exposed to thiouracil (TL) and of those returned to water at the end of seven days (TL-W) compared with the characteristic curve of water controls (W). concentration of the chemicals revealed that, at this concentration, thiouracil was least effective in retarding growth, while phenylthiourea was most effective. A marked depression, approaching toxicity, followed continued exposure to both thio- urea and phenylthiourea, but a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 112 MARIE M. JENKINS. 68 II 14 17 TIME IN DAYS 20 23 FIGURE 2. Growth rate curve of planarians exposed to thiouracil (TL) and of those returned to water at the end of seven days (TL-W) compared with the characteristic curve of water controls (W). concentration of the chemicals revealed that, at this concentration, thiouracil was least effective in retarding growth, while phenylthiourea was most effective. A marked depression, approaching toxicity, followed continued exposure to both thio- urea and phenylthiourea, but a noticeable recovery was made when the animals were returned to water after a week's exposure. This, too, is in accord with the facts noted above. DISCUSSION In the present study, it was found that the normal regenerative powers of the planarians were reduced by the administration of goitrogenic agents in varying concentrations, and that the effect was more pronounced as the concentration was increased. This is in conformity with the findings of Lynn (1948) and Rulon (1950). Lynn, testing two of the thioureas on a toad, Eleutherodactylus ricordii, which possesses no aquatic larval stage, found that a concentration of thio- urea was ineffective, a concentration of was slightly effective, and that a concentration of thiourea caused a definite retardation in development. Rulon reported that continuous exposure of newly fertilized eggs of Dcndrastcr to low concentrations of thiourea resulted in slight inhibition of development, and that with higher concentrations the degree of inhibition Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biological Laboratory (Woods Hole, Mass. ). Annual report 1907/08-1952; Lillie, Frank Ratt
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
