370 G. HAROLD DREW 



experiments were made to eliminate the possibility of the origin of 

 the cihated epithelium lining the cysts from the ciliated cells of 

 the oviduct, which might be present in pieces of the ovary that 

 were implanted, or from the layer of epithelial cells forming the 

 outer coating of the adductor muscle, which might be carried 

 inwards by the transplanting needle. 



It thus appears that the conversion of fibroblasts into ciliated 

 epithelium is a specific reaction following the implantation of the 

 ripe living ovary. 



These observations are the result of nearly a thousand experi- 

 ments, of which the majority have been performed on Pecten 

 opercularis. 



DISCUSSION OF RESULTS 



It appears that the conversion into ciliated epithelium of the 

 inner layer of fibroblasts lining a cyst formed round a piece of the 

 ovary, which has been implanted into the adductor muscle of 

 Pecten, is a specific reaction that occurs only when the ripe liv- 

 ing ovary of an animal of the same species is implanted. The 

 reaction takes place long after all trace of orga-iised structure 

 in the implanted tissue has disappeared, and it is difficult to con- 

 ceive of its being due to any other cause than the presence of some 

 definite chemical substance within the cyst, which is character- 

 istic of, and specific for, each species. It cannot well be a fluid 

 existing preformed in the ova, as in this case it would soon escape 

 through the reticulate and easily permeable layer of fibroblasts 

 first formed round the implanted m'ass, and for the same reason, 

 considering the relatively great length of time necessary for the 

 reaction to occur, it is not probable that it is a fluid formed at 

 one definite stage in the process of degeneration. If a fluid at 

 all, it seems on these grounds likely that this substance is slowly 

 and continuously formed for a considerable period within the cyst. 

 Examination of the contents of the cysts shows in all cases where 

 the development of ciliated epithelium has occurred, that an or- 

 ange granular substance, and blood corpuscles in various stages of 



