Genetics: P. T. Ives

the genetic constitution of the implant itself as well as the relative stages of development of implant and host may also influence this property of autonomy or non-autonomy of the implant. As a concluding example, we shall mention briefly, experiments made to establish the time in development at which vermilion pigmentation is irreversibly determined, i.e., after which a vermilion eye disc implanted in a wild type host will no longer give wild type pigmentation. By implanting eye discs from v pupae of successively older stages in wild type larvae almost ready to pupate (this procedure was used because of technical difficulties in implanting eye discs in pupae), it was shown that the characteristic host-implant influence operates, under these conditions, until very late stages, until about 48 hours after the formation of a puparium (at 250C.). Shortly after this time, actual pigment can be seen in the. eye. Details of the above-mentioned experiments, as well as a description of the technic, will be published elsewhere.