EXPERIMENTAL METAPLASIA 369 



and the cyst wall consisted only of fibrous tissue. If a thoroughly 

 ripe and healthy looking ovary be used, and sepsis does not occur, 

 it can be said with certainty that all surviving over thirty days will 

 develop ciliated epithelium lining the cysts. 



SUMMARY OF RESULTS OF EXPERIMENTAL WORK 



The implantation of small pieces of the ripe ovary of Pecten 

 maximus or Pecten opercularis into the adductor muscle of an- 

 other animal of the same species results at first in the formation 

 of a closed cyst within the muscle, lined with layers of fibroblasts. 

 Complete degeneration and disintegration of the ovarian tissue 

 within the cyst occurs in a few days, and then the cyst contains 

 only an orange colored granular substance, presumably derived 

 from the yolk, and numbers of blood corpuscles. After the lapse 

 of from 21 to 32 days, changes occur in the innermost layer of fib- 

 roblasts lining the cyst, they revert to an embryonic type, and 

 afterwards become converted into columnar ciliated epithelium, 

 which forms a continuous layer hning the cyst. The changes 

 resulting in this formation of ciUated epithelium from fibroblasts 

 can be followed clearly step by step, and once formed, the ciliated 

 cells persist unaltered for at least 120 days, which was the longest 

 period for which the animals could be kept alive in the experi- 

 mental tanks of the Laboratory. 



Experiments were performed showing that this change is not 

 produced by the implantation of any of the other tissues of Pec- 

 ten, by neutral foreign bodies which would merely act as a source 

 of mechanical irritation, by the transplantation of the ripe ovari- 

 an tissue of other Lamellibranchs, or by the transplantation of 

 pieces of the ovary of Pecten opercularis into the adductor mus- 

 cle of Pecten maximus and vice versa. 



Other experiments showed that the development of ciliated 

 eoithelium does not occur if pieces of the immature or spent 

 ovary be implanted, and that it is prevented by treating the ripe 

 ovary with a suspension of the sperm in sterile sea water before 

 implantation. Also that it does not occur if the ovary be killed by 

 physical or chemical agents before implantation. A series of 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 10, NO. 4 



