72 HENRY LAURENS AND J. W. WILLIAMS 



Eyes were transplanted in frog tadpoles (Rana palustris) as 

 well as in Amblystoma larvae, the stage of development used for 

 the operations being that when the tail bud is just beginning to 

 be perceptible (Laurens '14). The optic vesicle was removed 

 and transferred to the slightly enlarged cavity made by re- 

 moving the auditory vesicle. All transplants were made on the 

 left side, the right eye being left to serve as a control. For 

 some reasons all but two of the tadpoles died, before they reached 

 a length of 30 mm. Sections of the transplanted eyes of the two 

 survivors, killed just before metamorphosis, showed essentially 

 normal conditions. It is planned to repeat the experiments on 

 tadpoles for the reason that they will in all probability show even 

 greater reactions and more extensive changes, as indicated by the 

 results on normal eyes, than are to be reported now on the eye 

 of Amblystoma. 



It is known from the work of Lewis and others that the trans- 

 planted optic vesicle of the Amphibian will develop into essen- 

 tially a normal eye. Uhlenhuth ('13, '13 a and '13 b) has shown 

 that the same thing is true of the eye when it is transplanted in 

 larval stages after its differentiation is far advanced. We have 

 found in Amblystoma that the eye developed from the trans- 

 planted optic vesicle is essentially normal, all the elements being 

 present with the same relative number of rods and cones. There 

 are certain differences, however, to be noted. In the first place 

 the characteristic form (to be described later) of the rod nuclei 

 is lost, and secondly the number of ganglion cells is much less 

 than in the normal eye. The optic nerve also has never been 

 observed to be present. Moreover the orderly arrangement in 

 two separate rows of the rod and cone nuclei is sometimes, though 

 not always, disturbed. 



In figure A a view of the anterior end of an Amblystoma larva, 

 31 mm. long, is given to show the general position and appear- 

 ance of the transplanted eyes. In figure B a section of such an 

 eye is shown. 



