There have been many investigations on the effect of administration of anterior lobe pituitary preparations on the metamorphosis and sexual development of Amphibia, but so far as can be ascertained no similar work has been done on lampreys. These animals live for several years buried in the mud as ammocoete larvae and eventually metamorphose abruptly, changing their shape and colour and acquiring eyes and a sucker. Various workers have attempted without success to produce this change by injection of iodine or thyroid extracts (Remy, 1922; Horton, 1934).

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