ize them artific 

 does not chang 



ch inverted eg* 



normal egg with black |>«.le uppermost. 



An entirely different problem was also solved by the 

 method. Seventeen eggs fixed in normal positions and 

 three days till the neural groove and ridges were formed, 

 the direction of the median plane of the future frogs, 

 plane of the first cleavage furrow having been prevr 

 indicated by lines on the glass the eggs were stuck to, il 

 found that in twelve cases the median plane of the ar 

 coincided with the first cleavage plane, in four it mad 

 angle of 30°-60° and in one an angle of 90°. 



gravi 





second paper 3 that normal larva' both of Ham* txrnlnttn and of 

 Bombinator ignens were raised from eggs held inverted as well 

 as some larva? partly white on the dorsal surface and not 



The medullary folds, normally upon the black pole, may be 

 made to appear upon the white pub' by inclining the egg axis. 

 The author concludes that the egg is directed by gravity so 

 that cleavage may take place in various planes of the egg 

 according to the position of its axis with reference to the lines 

 of gravitation or vertical plane. Moreover, these effects are 

 seen later, the author thinks, in the origin of the blastopore 



