Compensatory Regulation. 



59 



'M 



m 



I 



which cuts were made in my experiments is shown in the accom- 

 panying figure. In none of them did the functional operculum 

 changt its character or did any 

 structure other than a rudimen- 

 tary operculum develop in place 

 of the old rudimentary. (Fig. 

 19B, a-c.) 



e. Operations on Both Oper- 

 cula. When both opercula were 

 cut off it was found that while in 

 some cases there was a reversal, 

 in others two functional opercula 

 were developed, one on each side, 

 while in still others characteristics 

 differing from either of these two 

 combinations were formed. An 

 attempt was made to find the 

 cause of the difference in results 

 and with this object in view cuts 

 were made at different levels. 

 The difference of level in the cuts 

 in the rudimentary operculum 

 could not be easily controlled, 

 but since in the former cases 

 where only the rudimentary oper- 

 culum was removed there was 

 no specific influence either on the 

 opposite functional operculum or 

 on the new regenerating one, it is 

 supposed that these differences of 

 level have here also no influence 

 upon the character of the result. 

 In every case care was taken to 



// 



/// 



/y 



bring the cut well down toward 



Fig. 21. 



Hydroides dianthus (X 30). Operations made 

 on both opercula simultaneously. I, II, III, IV 

 represent the regions of functional operculum in 

 which the cuts of the four groups of experiments 

 were made. The shaded portion of the rudi- 

 mentary operculum between the two dotted 

 lines includes all the cuts on this side. 



summar 



the base of the rudimentar) 



operculum. The different levels 



on the functional operculum are indicated in Fig. 21. A 



of the results is made in Table VIII. 



If we neglect the differences in the levels of the cuts in the rudi- 

 mentary operculum and divide those of the functional one into 



y 



