BEHAVIOR OF CELLS IX FUNDULUS HETEROCLITUS. 22Q 



Pigment Cells. Chromatophores of fundulus are large cells 

 containing either black, brownish red, or yellow pigment granules. 

 The cells migrate readily from the explant, but do not as a rule 

 travel far. Stockard ('15) show r ed that the chromatophores 

 have an affinity for plasma-filled spaces, being found adhering 

 to the pericardium in normal embryos and to the heart itself in 

 embryos deprived of a circulation. In the cultures of fundulus 

 brown chromatophores were several times observed closely 

 adhering to the beating heart, which happened to be projecting 

 out into the fluid medium. Here they remained elongated for 

 several days until the cultures degenerated. Isolated pigment 

 cells that had wandered out upon the membrane degenerated 

 more rapidly than other kinds of cells, and the pigment granules, 

 freed from the cells, were readily taken up by the mesenchymal 

 cells where they became aggregated around the nucleus (Fig. 6). 



In addition to the pigment cells and those forming a membrane 

 or reticulum other types of mesenchyme cells were observed. 

 Among these were certain denser, more granular and vacuolated 

 cells which migrated out upon the mesenchymal reticulum, and 

 other cells (probably clasmatocytes) with brighter, more solid- 

 looking protoplasm and numerous curved, finger-like pseudo- 

 podia. These cells contained numerous granules often derived 

 from degenerated chromatophores. Brownian movement of 

 these ingested granules was frequently observed. 



Yolk Cells. In some explants certain peculiar spherical cells 

 filled with numerous clear greenish yolk spheres were seen massed 

 together in the anterior part of the digestive cavity. These 

 cells migrated readily out upon the mesenchymal reticulum 

 where they became very slowly amoeboid and wandered out 

 along the edge of the ectoderm. Fig. 7 shows a group of these 

 cells with the yolk spheres stained deep black with iron haema- 

 toxylin. 



Cell Division. The appearance of new cell boundaries in the 

 ectoderm was frequently observed but in no case was a cell seen 

 to divide. There is therefore no evidence as to whether the 

 cells divide by mitosis or amitosis. In over fifty cultures stained 

 with iron haematoxylin no stages of mitosis were observed. Two 



