8o 



Charles Zeleny. 



branchial stage before showing even a beginning of an opercular 

 knob, in the other case where only the anterior two or four seg- 

 ments remain the operculum appears as such from the start. 



Unfortunately the animals in the last two lots did not live long 

 enough to show whether or no the final outcome would have been 

 the same in the two cases. In fact none of them showed any 

 pinnules on the branchiae at the time of death. Notwithstanding 



Fig. 26. 

 Apomatus ampullifera. Regenerating branchial circlets. Nine days after operation ( X 40). 

 Operation: Autotomy of both branchial circlets at breaking joint and removal of body posterior to 

 second thoracic segment. Note pronounced opercular differentiation on both sides. 



these limitations it is evident that we have a definite acceleration 

 of the rate of differentiation of the opercula. 



Two probable factors may be mentioned as concerned in the 

 bringing on of the acceleration, i. The shock of the transverse 

 division of the body may lead to such an increase in rapidity of 

 differentiation. 2. The small size of the piece itself may directly 

 influence the process and bring about such a differentiation. This 

 action may result because of the difference in the interactions of the 

 organs in the one case as compared with the other. 



