2IO 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



Figure 82. The two series are very similar in that the secondary modifica- 

 tions are limited to the apical region. Position of the mouth at one side 



Fig. 82. — Slight differential recoveries in Arabacia after relatively extreme inhibition by 

 various agents (from Child, i9i6(/). 



in some, presumably the ventral side, of the apical outgrowths suggests 

 that a trace of ventrodorsality is still present apically; but there is no 

 evidence of it elsewhere. In others, however, the mouth is apparently 

 apical, suggesting possible induction of a mouth by the entoderm. Degree 



