DEVELOPMENTAL CHANGES OF PIECES OF FROG 

 EMBRYOS CULTIVATED IN LYMPH. 



S. J. HOLMES. 



In the course of some experiments on the behavior of the 

 epithelial tissue of frog embryos when cultivated in lymph or 

 plasma it was found that pieces of tissue sometimes underwent 

 developmental changes. During the comparatively short time 

 in which material was available for experimental work, oppor- 

 tunity was not found for devoting as much attention to the 

 changes in these pieces as was desirable. Nevertheless a few of 

 the things observed were sufficiently striking and suggestive to 

 be worthy of record, and it is hoped that the observations may 

 be made more complete at a future date. 



The material used consisted of embryos and young larvae of 

 Rana taken out of the jelly a short time before they w r ere ready 

 to make their natural exit. The jelly was placed for a few min- 

 utes in an antiseptic solution, and the embryos were afterward 

 cut to pieces in sterile Ringer's solution. Each piece was then 

 mounted in a hanging drop of lymph or plasma of the adult frog, 

 sealed up in a hollow slide, and kept in a cool place. Every few 

 days the piece was transferred to a fresh medium. 



Changes in the ectodermic epithelium were quite manifest a 

 few hours after the pieces were mounted, and in one or two days 

 remarkable strands and sheets of ectodermic cells were to be 

 seen extending into the culture medium. These structures and 

 the behavior of their component cells are more fully described 

 in another paper now in course of publication. But aside from 

 the movements of the ectoderm, there were, in certain of the 

 pieces, marked developmental changes of the internal parts. 

 Irregular fragments of tissue frequently became more rounded 

 in form; sometimes they put out lobes or processes of various 

 kinds, and, in some cases, they increased noticeably in size. In 

 a piece from the head region of a late embryo shortly before the 

 rudiments of gills made their appearance, there were developed, 



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