258 



HUBERT B. GOODRICH. 



contract completely to a spherical form and then gradually 

 expand. 



i V 



2.44 



100 MICRONS 



FIG. 9. The history of a bipolar fan cell for one hour and eleven minutes at 

 room temperature of 23. Movement is by method of alternate expansion and 

 contraction. For details see text. 



The cells having fans were found only in cultures showing 

 epithelial growths such as described by M. R. Lewis ('16) and 

 Dederer ('21). I have planted cultures from embryos of various 

 stages but have been unable to obtain this type of growth from 

 those of less than six days of age when developing at the tempera- 

 ture of the running sea water in the laboratory (19 to 22). The 

 most favorable period for planting and obtaining such growths is 

 shortly before hatching (about 17 days, !9-22). Sections of 

 embryos of these later stages reveal a conspicious layer of cells 

 beneath the surface epithelium which are almost completely 



