356 GRADIENT-FIELDS IN POST-EMBRYONIC LIFE 



dsl Dorsal 



si gr. t hf gr. e 



Dorsal 



Ventral 



gr.e 



gr. I 



Dorsal 



'— si 



Ventral 

 Fig. 171 

 Modification of gradient-fields in grafted tail-fragments of frog tadpoles. The 

 tip of the tail was removed in the embryo and regrafted upside down. When 

 smooth healing occurred (as in lower figure) the lateral-line growing down from 

 the trunk assumed a position normal for the intact organism on the dorsally 

 directed (originally morphologically ventral) side of the muscles of the grafted 

 piece. When, however, much scar-tissue was formed (as in upper figure) the 

 lateral-line grew along the morphologically dorsal side of the muscles of the graft, 

 i.e. in relation to the field-system of the graft, not of the organism as a whole. 

 ch, notochord; med, neural tube;^r.e, line of fusion of epidermis; gr.t, line of 

 fusion of myotomes ; /?/, fold in fin ; si, lateral line ; dsl, dorsal branch of lateral 

 line. (From Harrison, Arch. Mikr. Anat. lxiii, 1904.) 



