210 HUBERT DANA GOODALE 



of their stain, while at either side, no loss occurs. Before cell- 

 walls become numerous, the stain slowly spreads from granule 

 to granule for a considerable distance, though sometimes it fol- 

 lows the cleavage furrows. After the egg becomes well divided 

 into cells, this indefinite spreading largely ceases, apparently 

 because the stain does not easily diffuse through the cell walls. 

 The stain does not injure the egg unless an excessive amount 

 be applied. If this is done, the egg, after a time presents a sort 

 of burned spot in the places where the concentration of stain has 

 been too great. Such injured places are relatively permanent, 

 especially when the injury is considerable. As they do not seri- 

 ously affect the further development, they are often of advantage 

 rather than otherwise, especially when, as in my experiments, 

 they lie in regions not subject to movements of the egg material, 

 thus furnishing a check upon. the movements of the stained spots. 

 A large number of other aniline dyes have been tried. Most 

 were entirely unsuitable. Chrysoidin produces a yellow mark 

 which does not spread, but fades out in about twenty-four hours. 

 It has been used in some of the studies of the movement of the 

 blastopore. Further trials may show some stain lacking the 

 faults of Nile blue. 



Method of staining the living egg 



A very definite mark can be made upon the egg in the early 

 cleavage stages, if it is first shelled out of its envelopes, but such 

 eggs sooner or later disintegrate. The egg cannot be marked 

 as it lies within its intact envelopes, so the following method was 

 adopted. The egg is placed on a glass slide and the outer jelly 

 is stripped off with needles leaving the inner capsule intact. 

 Surplus water is removed and the inner capsule punctured with 

 a sharp needle, taking care not to injure the egg. This allows 

 the perivitelline fluid to escape. All fluid about the egg is care- 

 fully removed with filter paper, and the least possible amount of 

 dry stain is then applied with a needle in the desired position on 

 the jelly. When a sufficient number of places have been marked, 

 the egg is set aside for a few moments, care being taken to see 



