406 WILLIAM H. COLE 



5. Tail-skin and back-skin grafts over thin glass plates were 

 not regularly absorbed. The foreign material is not the stimulus 

 for absorption. 



6. The absorption of tail-skin grafts over normal eyes, as well 

 as over the convex 'artificial eyes/ is caused by the curvature of 

 the eyeball or of the artificial eye, respectively. The more com- 

 pact structure of back skin prevents the absorption of back-skin 

 grafts. The curvature of the graft during the healing period 

 causes a tension, which is the mechanical stimulus for absorption. 



7. In direct contrast to back-skin grafts, all tail-skin grafts 

 proliferated new tissue. In some cases miniature tail tips were 

 formed, while in others amorphic regeneration predominated. 

 The anterior ends of such grafts, as well as the posterior ends, 

 are able to regenerate a tail tip containing notochord and nerve 

 cord. 



8. Following the proliferation period, all grafts enter a state of 

 equilibrium in which there is no increase in their size. 



9. There is, therefore, no functional regulation of skin grafts 

 over eyes. This lack of correlative regulation is the result of 

 the high state of differentiation and specificity attained by the 

 skin and the eye. 



B. Local specificity of integument 



1. Integument from the tail, back or belly transplanted to 

 another region of the same animal preserves its individual 

 characteristics indefinitely. 



2. Homoiotransplants of integument preserve their individ- 

 uahty only temporarily, their tissues ultimately being replaced 

 by regenerated tissue of the host. 



3. The integument of frog tadpoles is therefore locally specific, 

 and is seK-differentiating when transplanted to new soil on the 

 same animal. 



C. Acquisition of melanophores by white grafts on a black region 



1. Autotransplants and homoiotransplants of white belly skin 

 on the back or tail region acquire melanophores. 



