The Influence of External Factors on Development 197 



one or two hours do not recover from the effects of this treatment 

 after being returned to sea-water. Many other facts go to show 

 the readiness with which this membrane is permeated. 



2 Fundulus eggs develop normally, although at a somewhat 

 faster rate, when kept on moist plates entirely out of water. 

 The embryos developed out of water are unable to hatch while on 

 the moist plates, but if at any time after the control has begun 

 hatching some of the eggs are immersed in sea-water they will soon 

 begin hatching, commencing usually in about ten minutes after 

 being in the water and all coming out very promptly. On hatching 

 the embryos show a positively heliotropic and a negatively geotro- 

 pic reaction. 



Embryos were kept for thirty-three days, or twenty days after 

 the control had begun hatching, on these moist plates without 

 beginning to hatch. The fish within the egg membrane grows in 

 length and absorbs its yolk at about the same rate as hatched ones 

 do. They finally die of starvation after having assimilated all of 

 their yolk, being still confined within the egg membrane. 



3 Fundulus eggs are not entirely immune to osmotic effects 

 though it has often been stated that they are. In weak cane sugar 

 solutions the yolks were observed to swell, this has never bepn seen 

 even in eggs developing in distilled water and may probably be due 

 to some change taking place in the sugar after it has permeated the 

 egg membrane. In concentrated sugar solutions the yolk shrinks 

 in a somewhat definite manner. A 1.53 m distilled water solution 

 of cane sugar killed the eggs within twenty-three hours. The osmo- 

 tic pressure of such a solution is calculated to be 34.278 atmos- 

 pheres or about twelve atmospheres more than that of sea-water. 

 Some salt solutions which exert even a greater pressure do not kill 

 the eggs. This contradiction might be explained if the cane sugar 

 becomes inverted in the solutions but from the evidence at hand 

 this interpretation seems improbable. There may possibly be an 

 action of the new substances resulting from the inversion of the 

 cane sugar molecule which is also injurious to the eggs. 



Eggs hatch in 0.166 m solutions of sugar in sea-water. On com- 

 paring the effects of sea-water solutions of sugar with distilled 

 water solutions it was found that a pressure more than double as 



