ORIGIN OF 'independent' LENSES 361 



substance. In a similar manner we may perhaps yet succeed 

 in obtaining identical results in those amphibian species which 

 at present form the vexing exception to the rule of the depend- 

 ent differentiation of the lens. The chemical method has some 

 advantages over the most refined mechanical method of experi- 

 mentation. Might it not perhaps, if employed on amphibian 

 eggs, help to harmonize the contradicting results of the experi- 

 ments with mechanical methods? Judging from results of some 

 preliminary experiments^ which I have performed with acetone 

 solutions on frog eggs, I am inclined to think that blastolytic 

 teratophthalmia can in these eggs also be produced. And it 

 seems safe to expect that free lenses which so often occur in 

 teratophthalmia, may also be found in such teratophthalmic 

 amphibian embryos. I venture to predict that results similar to 

 those in the embryo here described may be obtained, if weak 

 solutions of acetone and long exposures be employed. 



Another possibility for the origin of free lenses in terato- 

 phthalmic embryos is suggested by the retinal lentoid of our em- 

 bryo (fig. 5). I regard the latter as a tissue heteromorphosis due 

 to a local chemical injury of the potential retina. This injury 

 may not be strong enough to destroy the pf.rt affected, but 

 rather it may consist in so decreasing by chemical alteration its 

 chemomorphic potentiality as to cause its ultimate differentia- 

 tion into a structure less complex than it was 'destined' to form. 

 This embryonic heteromorphosis has its analogue in the regen- 

 erative heteromorphosis presented by Fischel's ('02) retinal len- 

 toids, the differentiation of which resulted from mechanical in- 

 jury of parts of the retina. It would seem not improbable that 

 in Fischel's experiments, too, chemical alteration which resulted 

 from the mechanical destruction has so decreased the chemo- 

 morphic capability of the injured parts of the retina that the 

 potency for hypotypical regeneration (lentoids) only has re- 

 mained. However this may be, it is evident that optic cup sub- 

 stance may under certain circumstances develop into bodies of 

 lens-like structure. If we now recall the fact that eye terata re- 

 sult from blastolytic injury of the potential optic cup, it is easy 



5 Not published. 



