GLYCOGEN IN CELLS OF EMBRYOS. 245 



staining. Thus it is seen that some substance, which reacts as 

 does glycogen when exposed to iodine, is present in the cells of 

 fundulus cultures. It is possible that this substance is glycogen. 

 That the substance which became port-wine colored was not 

 the dextrose itself is shown by the fact that dextrose placed in 

 Locke's solution did not so stain when exposed to iodine, while 

 glycogen did. 



A few cultures of chick embryos were tested in the same 

 manner for a comparison with those of the fish embryos. No 

 port-wine color was observed in the cells of the older embryos 

 except in one somewhat degenerate culture where a few blebs 

 were already present on certain of the dying cells; these blebs 

 became slightly pink but in no case was there the port-wine 

 coloration such as occurs in fundulus cultures. On the other 

 hand the cells in cultures of very young embryos (48 hours) 

 sometimes contained an abundance of this substance. 



THE INFLUENCE OF STARCH UPON THE AMOUNT OF 

 GLYCOGEN PRESENT IN THE CELLS. 



Soluble starch (Kaulbaum) was added to the medium of the 

 cultures of fundulus embryos in order to determine whether it 

 could be utilized by the cells to store up glycogen. The starch 

 was dissolved in distilled water and boiled for two minutes; 

 60 c.c. of the starch solution was then added to 40 c.c. of sea 

 water and the medium prepared in the same manner as for 

 normal cultures. When the quantity of starch was less than 

 o.i per cent, it had no appreciable effect upon the cells. In 

 these cultures the growth was normal and no increase in the 

 amount of glycogen could be detected. When larger amounts 

 of starch were added, or when the starch became slightly clumped 

 into masses of very small granules, as sometimes happened, small 

 particles were occasionally taken up by the cell and appeared 

 within the cytoplasm as small granules or granular masses, in 

 some cases surrounded by a vacuole. Upon exposure to iodine 

 the starch became blue, whether within the cell or in the medium. 

 The surrounding vacuole became pale blue, or sometimes lilac, 

 but never the port-wine color indicative of glycogen. The port- 



