A DESCRIPTIVE SKETCH 



dorsal 



23 



ventral, 



;;S^'''Eg 



dorsal 



Map of the presumptive regions of the Urodele embryo, projected on to the sur- 

 face of the blastula, as seen from the vegetative pole and from the left side. 

 Epidermis, sparse broken lines ; neural plate, dense broken lines ; notochord, dense 

 dots; mesoderm, fine dots; endoderm, white. The future mesoderm segments 

 are numbered. Eg-Eg, limit of invaginated region ; J, site of formation of first 

 invagination; K, gill-pouches; Sch, tail region; Spl, lateral plate mesoderm; 

 u, position of future blastopore lip ; uP, lowermost pole at this stage ; Vii.Ex, fore- 

 limb; vP, vegetative pole. (From Vogt, Arch. E?itzvviech. cxx, 1929.) 



