*'* EYE FIELD OPERATIONS 



(from which the lens was derived) then closes over the lens to form the ectodermal por- 

 tion of the (transparent) cornea. In the meantime mesenchyme (mesoderm) invades the 

 whole eye structure, to give rise to the blood vessels, connective tissue, and finally the 

 muscles of the eye. 



That the mesentodermal substrate has something to do with the development of the eye 

 field has been demonstrated (Adelmann, 1937). This eye-field is determined prior to the 

 closure of the neural folds, as proven by excision and transplantation experiments. 



In the heteroplastic and homotopic eye transplantations involving A. punctatum, A. tigri- 

 num, and A. mexicanum (the axolotl) Harrison (1929) has demonstrated that the velocity 

 of growth and, to a certain extent, the ultimate size of the eyes are due to intrinsic 

 (genetic) factors of the donor tissues. The tigrinum eyes in punctatum hosts often ex- 

 ceeded the donor control eyes, and the punctatum eyes in tigrinum hosts often were 

 smaller than the control eyes, explained by Harrison as due to factors in the circulating 

 medium of the host which affected the growth rate of the graft. The form and function of 

 the grafted eyes appeared to be quite normal. Even the intrinsic tendencies of the lens 

 and/or the optic vesicles were maintained when in grafts, when they were from different 

 genetic sources. In all cases where the optic nerve failed to connect, there was marked 

 hypoplasia of the wall of the midbrain on the opposite side. 



Schwind (1937) has shown that heteroplastic eye grafts between three species of Rana in- 

 variably failed to develop. Eakin and Harris (1945) used the optic vesicle as a test object 

 in some xenoplastic transplantations between Urodele donors and Anuran hosts. Grafts 

 from Triturus or Amblystoma donors to Hyla hosts never survived for very long, and 

 were eventually destroyed, generally within a week. They state that "Incompatability be- 

 tween host and xenoplastic transplant is regarded as a humoral and cellular antagonism 

 of the host in response to alien substances which diffuse out of the graft into the body of 

 the host. " 



That the eyes have not lost their power of adjustment has been demonstrated recently by 

 Stone and his co-workers (Stone & Ellison, 1945) by the exchanging of eyes between adult 

 salamanders of different species. There is apparently a regression of the morphology 

 and physiology of the eye and a recovery of both the normal structure and function, even 

 in the adult eyes. 



REFERENCES 



ADELMANN, H. B. , 1936 - "The problem of cyclopia. " Quart. Rev. Biol. 11:161 G 284. 



ADELMANN, H. B. , 1937 - "Experimental studies on the development of the eye. IV. The effect of the partial and complete 



excision of the prechordal substrate on the development of eyes of Amblystoma punctatum. " Jour. Exp. Zool. 75:199. 

 ALDERMAN, A. L. , 1938 - "A factor influencing the bilatemlity of the eye rudiment in Hyla regilla. " Anot. Rec. 72:297. 

 BALLARD, W. W. , 1939 - "Mutual size regulation between eyeball and lens in Amblystoma, studied by means of heteroplastic 



transplantation." Jour. Exp. Zool. 81:261. 

 DETWILER, S. R., 1944 - "Behavior of Amblystoma larvae lacking in forebrain, eyes, and nasal placodes." Proc. Soc. Exp. 



Biol. G Med. 56:195. 

 DETWILER, S. R. G W. M. COPENHAVER, 1942 - "Further experiments dealing with embryonic enucleation in Amblystoma. " 



Proc. Soc. Exp. Biol. G Med. 51:334. 

 DINNEAN, F. L. , 1942 - "Lens regeneration from iris and its inhibition by lens reimplantation in Triturus torosus larvae." Jour. 



Exp. Zool. 90:461. 

 DRACOMIROV, W. , 1935 - "Determination des Augenkeimes bei Amphibien. " Acad. Sci. d. Ukraine, Trav. Inst. Zool. et 



Biol. 8:25 (see also 1933 Arch. f. Ent. Mech. 129:522). 

 FILATOW, D. , 1937 - "Uber die Linseninudzierung nach EnJjrnung des Chorda -mesoderms bei Rana tempororia. " Zool. Jarb. 



Abt. allg. Zool. u. Physiol. 58:1. 

 GREENE, W. F. G H. LAURENS, 1923 - "The effect of extirpation of the embryonic ear and eye on equilibration in Amblystoma 



punctatum." Am. Jouf. Physiol. 64:120. 

 HALL, T. S. , 1942 - "The mode of action of lithium salts in amphibian development. " Jour. Exp. Zool. 89:1. 

 HANDFORD, S. W. , 1945 - "The relation of age and temperature to the relative growth of the eyes of Amblystoma. " Jour. Exp. 



Zool. 98:127. 



