EXPERIMENTAL FISH EMBRYOLOGY ^01 



DRAWINGS AND RECORD OF FISH EXPLAMTS IN VITRO 



Yamamoto (1959 Fac. Scl. Tokyo Univ. 15:269) gives a formula for a synthetic medium 



which is isotonic to the Oryzias egg. 



M/7.5 NaCl 100 oc. 



M/7.5 KCl 2.0 cc. 



m/II CaCl^ 2.1 cc. 



pH to 7.5 



To such a medium 0.1^ glucose may he added for nutrition for the explants of Oryzias. 



Hayes, Darcy and Sullivan (l9'+6: Jour. Biol. Chem. l65-"621) have analyzed the ovarian 

 or coelomic fluid of the salmon, which fluid appears suddenly Just at the time of hatching. 

 They find it to he a clear, limpid, and slightly translucent medium with the following 

 constituents: 



Ions per 1,000 liter of water: 



Sodium 151 mllli equivalents 



Potassium 5-2 



Calcium 7 • 1 



Magnesimn 2.6 



Chlorine II6 .0 



HPOi^ 1+ . 



HCO5 : 13 .'+ 



Since the ripe eggs of the Salmon lie freely within the body cavity, and hence within this 

 fluid medium, this medium may he considered as isotonic to the eggs at this stage. This 

 fluid is, however, hypertonic to hlood. Sodium chloride is the dominant salt, with other 

 Ions in the approximate ratio that they are found in sea water. In the eggs the potassium 

 dominates, and the calcium and magnesium are not osmotically active. At fertilization, in 

 water, the egg loses osmotic pressure hy about 5^' During development the egg and embryo 

 take up calcium and sodium from the environment so that the final amounts are h and 3 times 

 the initial amounts respectively. Phosphorous intake is markedly increased, probably in 

 connection with sketeon formation. 



