172 Charles R. Stockard 



dently they had been prevented from hatching owing to their 

 inabihty to break through the egg membrane when out of water. 



On the fifteenth day none on the moist glasses had hatched, 

 with the exception of two which I feel sure came out on account of 

 too much moisture or water having been put about those that were 

 rather dry on the day previous. Thirty eggs were now put into 

 sea-water, three of which hatched after ten minutes, thirteen were 

 out in fifteen minutes, twenty-five in twenty minutes, while twenty- 

 seven of the thirty eggs had hatched within twenty-five minutes. 

 On hatching, the embryos swim directly to the top of the water and 

 to the side of the bowl nearest the brighest light thus showing a 

 negatively geotropic and a positively heliotropic reaction. 



At sixteen days old not an egg on the moist glasses had hatched, 

 with the exception of the two which had hatched three days before. 

 Twenty eggs were now placed in sea-water, the first one came out 

 after ten mmutes. It seems as a rule to require about ten mmutes 

 for the eggs to begin hatching and after this period they come out 

 very rapidly. Fifteen were out after fifteen minutes and all were 

 hatched after being in the water only twenty-seven minutes. On 

 the morning of the seventeenth day two of those on the moist glass 

 had hatched, but again an extra amount of moisture had been put 

 about the eggs on the previous day. 



When twenty days old, six days after hatching had begun, all of 

 the controls were hatched, those on the moist glasses were alive and 

 well, though none had hatched. An excess of moisture was added 

 to them while still on the glass and twelve embryos came out 

 within twenty minutes, the moisture was then drawn off and 

 hatching ceased. 



When twenty-six days old a few of the eggs began to die, three or 

 four out of fifty died on one glass. This was probably due to 

 want of food as at this time all of the yolk had been absorbed for 

 several days past as seen by comparing Fig. i of a newly hatched 

 control embryo twelve days old, with Fig. 2 of a moist glass embryo 

 hatched when eighteen days old {yk the yolk mass) . A comparison 

 of these two figures will also show how the embryos on the moist 

 plates have continued to grow and develop within the egg mem- 

 brane. When eighteen days .old one of these was equally as large 



