DIFFERENTIAL DEVELOPMENTAL MODIFICATION. Ill 253 



definite pattern. The apparent association of orderly arrangement of 

 chorda cells in a definite notochord with presence of a gradient in the 



Fig. ioi, A-E. — Bilaterally symmetrical forms of Corella resulting from differential in- 

 hibition (from Child, ig2-]d). 



Fig. 102, A-E. — Stages of metamorphosis of Corella. A, uninhibited; B-D, differentially in- 

 hibited individuals metamorphosing without hatching; £, metamorphosis of somewhat inhib- 

 ited individual after hatching but without development of tail at any stage (from Child, ig2'jd). 



developing tail and loss of definite arrangement when the caudal gradient 

 disappears is perhaps of interest. 



The more inhibited individuals very commonly attain more or less ad- 

 vanced stages of metamorphosis within the egg membrane (Fig. 102) and, 



