BEHAVIOR OF CELLS IN FUNDULUS HETEROCLITUS. 



227 



increased in extent, more striations became visible. The mark- 

 ings appeared to be on the under surface of the cells, that is, 

 farthest from the mesenchyme. The striae were very definite, 

 appearing as longer or shorter dark lines over the cell, varying 

 only slightly in width, and never crossing a cell boundary. The 

 wall between adjacent cells was distinctly double, so that each 

 cell had its own complete investment. This was also clearly 

 seen in a few cases where ectoderm cells had become separated 

 from each other. Frequently one or more striae near the periph- 

 ery of a cell were situated parallel with the cell wall, while the 

 inner ones were more irregular or arranged concentrically with 

 reference to several points in the cell. 



FIG. i. Camera lucida drawing of an ectodermal cell in process of flattening 

 out during migration; the central mass of thickened cytoplasm bordered by a 

 clear flat region with pale concentric markings. Ocular 5, lens 4 mm. 



Form and Behavior of Mesenchyme Cells. The mesenchyme 

 cells grew out from the explant as more or less elongated and 

 separate cells, which later became connected in various ways. 

 Adjacent cells sometimes sent out short broad processes along 

 their sides, which appeared to fuse with each other, forming a 

 reticulum with relatively small intercellular spaces (Fig. 9). 

 Characteristic also of these cells was the projection of their 

 protoplasm into short thread-like processes often giving a prickly 

 appearance to the edge. The prickly processes became converted 



