TO THE EMBRYOLOGY OF AMPHIBIA. 2o 



staut in this case, being rapid at the first and last observations 

 and quite slow in the interval. The acceleration in the first 

 instance was without doubt to be accounted for by the artificial 

 application of heat as the means of fixing the egg, while the 

 speed in the last period mentioned was perhaps due to the rise 

 of the atmospheric temperature. Such irregularities are, however, 

 of common occurrence and may be due to both artificial and 

 natural causes. 



By 3 p.m., of the same day, the dorsal lip had moved to 

 about 60° below the equator, and now the blastopore lip was 

 closed in a complete circle. At this time, the ventral lip was 

 found at a level 5° or 6° higher than the dorsal lip. In the 

 posterior view, also, there could be noticed some differences (2° 

 or 3°) in the level of the right and left lateral lips. The rim 

 of the blastopore was, therefore, in this egg somewhat wavy. 

 The highest part was at a point about 25°-30° to the right of 

 the middle line of the dorsal lip {i.e. of the blastoporic meridian), 

 showing that some trouble in the overgrowth of the lip had 

 unfortunately occurred in this region. When, however, I looked 

 at the egg at 6:30 p.m., all such unevennesses of the blastopore 

 lip had disappeared and it had now grown downward evenly all 

 around to about 66° below the equator. 



When seen at 7:30 on the next morning (the third day), the 

 blastopore had completely closed and the yolk-mass had been 

 withdrawn into the interior. The closure had taken place during 

 the night which was unusually warm. The point at which the 

 blastopore was closed was to be found about 30° to the right of 

 the former middle line of the posterior view, and moreover was 

 far below the equator (about 20°). Huch an irregularity was no 

 doubt due to the same cause as that which produced the uneven 



