248 BERTRAM G. SMITH. 



spot which will not wash out, and which is not toxic enough to 

 interfere with the normal development. The large size of the 

 egg (from 6 to 7 mm. in diameter), the ease with which it may be 

 removed from its gelatinous envelope, and the entire absence of 

 pigment make it a peculiarly favorable object for staining experi- 

 ments. From the behavior of the stain in experiments it appears 

 that it does not spread to any perceptible extent by diffusion, 

 and that stained areas are carried from one position to another 

 only by an actual movement of material. A very faint trail 

 may sometimes be left behind a moving spot, but this appears 

 to be due to secondary staining by the vitelline membrane. The 

 stain enables us to determine the direction and amount of the 

 movement of cells, and to distinguish an actual transference of 

 cellular material from a wave movement or undulation. 



My results with Cryptobranchns do not harmonize with Good- 

 ale's ('n) statement that in Spelerpes the yolk granules only are 

 stained. In the early cleavage stages of Cryptobranchus the 

 micromeres stain distinctly and keep the stain, while the more 

 heavily yolk-laden parts of the egg stain with difficulty and the 

 stain more readily washes out. In later cleavage stages the 

 micromeres stain more intensely than in the early stages, and 

 the neural folds take the stain with even greater intensity. The 

 inference would seem to be that the cytoplasm stains more 

 readily than the yolk. 



The method used in applying the stain to the egg of Crypto- 

 branchus is as follows: The egg is removed from its gelatinous 

 envelope and placed in water in a Syracuse watch glass. A small 

 drop of strong aqueous solution of Nile blue sulphate is applied 

 to its surface with a fine pipette. After an interval of about 

 half a minute the excess of stain is washed away and sucked up 

 with a clean pipette. On account of the large size of the egg, 

 magnification is not necessary. The under surface of the egg 

 may be viewed by means of a mirror placed under the watch 

 glass; the mirror is far enough away from the egg so that the 

 entire image may be observed at a single view. A lateral view of 

 the egg may be obtained by holding a piece of mirror in a vertical 

 position in the watch glass beside the egg. For purposes of 

 observation it is possible to turn the egg with a camel's hair 



