242 M. R. LEWIS. 



diluted (40%) sea water plus 0.02 per cent. NaHCO 3 plus 20 c.c. 

 fundulus bouillon plus 0.5 per cent, dextrose (M. R. Lewis, 1917). 

 Within 24 to 48 hours large growths were present around these 

 explants. The cells composing the growths were then exposed 

 to iodine vapor by scattering a few fragments of an iodine crystal 

 in the bottom of the hollow ground slide under the hanging drop, 

 care being taken to prevent them from touching the drop. The 

 vapor from the iodine crystal penetrated the hanging drop and 

 acted upon the cells. Just a sufficient amount of iodine should 

 be used to rapidly color the cytoplasm yellow and to show the 

 port-wine color of the glycogen within one to two minutes. 



NORMAL FUNDULUS CULTURES. 



As has been shown by Dederer (1921), the ectoderm and the 

 mesenchyme cells grow out from explants of fundulus embryos 

 in the form of membranes. The mesenchyme cells are usually 

 attached to the cover-slip and the ectoderm cells form a layer 

 directly beneath them. Mesenchyme cells extend beyond the 

 ectoderm and also along the edge of the membrane and those 

 scattered farther out on the cover-slip are the only cells which 

 have processes to any extent. These processes usually spread 

 out at one end into a large, thin, fan-like structure. One or 

 more large, flat, oval cells, probably endoderm, are sometimes 

 found on the membranes; these are quite different from the 

 mesenchyme cells, in that they have an oval shape while the 

 mesenchyme cells are elongated or somewhat hexagonal, and their 

 cytoplasm also appears to be of a different consistency. For 

 convenience of description these cells will be called oval cells. 

 When the cultures were placed over fragments of an iodine crystal 

 the cytoplasm and nucleus of all the cells became yellow, the 

 the mitochondria a darker yellow, and the fat globules a brownish 

 color. Almost the entire cytoplasm of the oval cells, regions of 

 the cytoplasm of some of the mesenchyme cells, and certain 

 parts of a number of their processes turned a port-wine color. 

 This was a distinctly different tint from that exhibited by any 

 other part of the growth and was the same as the characteristic 

 color exhibited by glycogen when exposed to the action of iodine. 



