Studies on Regulation. 497 



of the contents was eliminated the whole apparatus was regener- 

 ated in small size and more or less rudimentary form as above 

 stated. But in these experiments the physiological condition of 

 the regenerating specimens as regards sexual activity was the 

 same as in the cases where complete regeneration of the genital 

 apparatus occurred. The only difference is that in the one case 

 all parts of the ducts and all or nearly all of the gonads were 

 removed and there was no possibility of the extreme functional 

 activity of the ducts until new gonads were formed and matured, 

 a process which did not occur in the specimens without food. 



In many of my earliest experiments (August) no genital area 

 was observed in the regenerated specimens, though it may have 

 been present in some cases. But later in the autumn, as the breed- 

 ing period approached its height, the genital area appeared in all 

 cases. This difference indicates that there was some physiologi- 

 cal difference between the specimens at different seasons, a differ- 

 ence undoubtedly correlated in some way with the reproductive 

 organs. 



In the case shown in Figs. 28-30 it is interesting to note that 

 regeneration of the ducts apparently occurred partly within the 

 old tissue and partly within the new. During the course of 

 regeneration the cut end of the pharynx was gradually retracted 

 from the cut surface, leaving a space behind it in which the copu- 

 latory organ appeared. This contraction of the pharynx is 

 probably essentially atrophy from disuse; it occurs only in pieces 

 without ganglia. The region posterior to it is filled in either by 

 cells which have migrated or flowed in from the sides or by pro- 

 liferated cells or probably by both, and in this the copulatory 

 organ appears. The posterior vasa deferentia extend a consider- 

 able distance anteriorly into the old part before they unite with the 

 anterior ducts and the whole system of terminal organs is situ- 

 ated much further anteriorly than originally (compare Figs. 28 

 and 30). The large size of the regenerated organs is undoubtedly 

 due to the large quantity of the sexual products contained in them 

 and entering them during the course of the experiments. The 

 retraction of the pharynx afforded space for growth, hence the 

 position and extent of the organs. 



