2o6 Mary Isabelle Steele 



differentiation of each is conditioned by their relative positions in 

 respect to each other, to the surface and to the old parts present. 



That the relation of the old tissues to the regenerating tissues is a 

 determining factor in the regenerating of the new structures has 

 been maintained by several workers. Child ('04) who especially 

 emphasizes the idea, says: "The fate of the new material must be 

 regarded as depending essentially upon its relation to the old 

 parts." That the regeneration of one structure may be dependent 

 upon the presence of another has been shown by Lewis ('04). He 

 found that a lens could be developed from any part of the ectoderm 

 of a frog embryo by transplanting the optic vesicle and allowing it 

 to come in contact with the ectoderm. In this case it appears 

 that the actual contact of the two tissues constituted a determining 

 factor and that the new conditions have arisen on account of the 

 new relations of the two tissues. 



From the instances referred to the following inferences may be 

 drawn — first, newly regenerated tissue is largely indifferent in 

 character; second, the differentiation of the new tissue is largely 

 conditioned by its relation to the old tissue. The above inferences 

 may be used in suggesting an interpretation of the special phe- 

 nomena under consideration. 



To begin, it is evident that the particular individual now being 

 considered exhibited a more than usual degree of physiological 

 and regenerative activity. In no other way could we account for 

 so much more new tissue than is ordinarily regenerated by a 

 stump of this length. The sections show that a large part of the 

 new tissue still presents an undifferentiated appearance, although 

 in certain regions differentiation has begun. Just above the cut 

 end of the old muscle band (Fig. 35) the new tissue appears 

 thickened, arranged in definite fibers and is apparently continuous 

 with the muscle band suggesting that connections between the 

 muscle and the chitinous covering of the eye had been reestab- 

 lished. 



Sections passing through the stump near its ventral side show 

 rudimentary ommatidia in process of development. Just why 

 ommatidia should appear on the side of the old stump is not at 

 first sight apparent. One possible explanation of this phenom- 



