EYE F lELD OPERATIONS 297 



has been accomplished, transplant the entire optic vesicle and over- 

 lying ectoderm of another donor to the excavated optic region of another host 

 (homotopic and heteroplastic transplemt) . It would he hest to make the first 

 attempts from A. tigrlnum to A. punctatum. 



Make the reciprocal transplant indicated in "B", i.e., from A. pianctatum to 

 A. tigrinum, including the entire optic vesicle and overlying lens ectoderm. 

 Make a I'arge "U" shaped Incision through the ectoderm covering the optic 

 vesicle of A. punctatum at stage #27, with the open end of the "U" (uncut mar- 

 gin) toward the anterior, remaining as a hinge. Deflect this flap of ectoderm 

 forward, and scoop out the optic vesicle, cutting it at the origin from the 

 hrain. Quickly remove the overlying ectoderm from a donor embryo optic vesicle 

 (same stage hut either A. tigrinum or A. mexicanum) and cut it out without 

 damage. Place it in the previously prepared host region, beneath the flap of 

 host ectoderm. So far as possible attempt to orient the donor optic vesicle 

 in the a&me position as the original host vesicle. 



DRAWINGS AND BECOED OF HETEROPLASTIC- HOMOTOPIC TRANSPLANTATIONS 



