284 RUTH STOCKING LYNCH 



four days of cultivation. In the majority death had occurred 

 by the sixth day; in some not until the ninth day (figs, la to If). 



Character of growth 



In their manner of growth, and to some extent in character, 

 the liver cells resemble endodcrmal cells from explants of the 

 intestine, although they grow out from the explant much less 

 readily and much less rapidly. The first liver cells appeared at 

 the edge of the explant in one of three ways: as individual pro- 

 jecting cells, as a small triangular sheet of cells, or as a long 

 narrow sheet along the margin of the explant (figs. 1, 3, 4). The 

 second arrangement was the most common. The cells shifted 

 somewhat and changed shape, drew back into the explant, or 

 extended farther out (figs. 3, 4). In many cases individual cells 

 or groups of cells became entirely isolated from the rest of the 

 growth, and would creep out some distance from it (figs, le, 24, 

 25) . These were usually greatly flattened and therefore afforded 

 an excellent opportunity to observe behavior and details of 

 structure. 



In the best growths, before degeneration set in, the membrane 

 had a fairly regular contour with a finely serrated edge (figs. 3, 

 4, 19). When degeneration began this edge became ragged, holes 

 formed in the body of the membrane, and the whole sheet began 

 to break up (figs. Id, le). In a few cultures this irregularity of 

 contour was present from the beginning (figs, la, lb). Many 

 growths obtained from explants made in the culture medium 

 plus trypan blue, were ragged and had numerous isolated cells. 



Relation of migration to other factors 



Age of embryo. Growth was obtained from explants of five to 

 sixteen day embryos, good growths from explants of five to 

 twelve day embryos. No migrating liver cells were obtained 

 from explants of embryos older than fifteen days. Seventy- 

 three series with a total of 450 cultures, were made from embryos 

 of five to twelve days' incubation. Of these 250 (55 per cent) 

 showed migration of liver cells and 91 (20 per cent) gave good 

 liver-cell growth. Nine series with 33 cultures were made from 



