1 86 Edwin G. Cofjklin. 



Quarter Embryos; Young Tadpole to Metamorphosis Stages. Fixed and Stained 



Preparations. 



Fig. 65. Left anterior and right posterior (diagonal) quarter embryos, dorsal view; spurted in the 

 4-cell stage, fixed 5 hours later. The anterior quarter shows thickened ectoderm cells, probably neural 

 plate, around the endoderm cells; in the posterior quarter are 8 muscle and 3 caudal endoderm cells. 



Fig. 66. Left anterior and right posterior (diagonal) quarter embryos from the right anterior side, 

 the dorsal pole being above; spurted in the 4-cell stage, fixed 22 hours later. In the posterior quarter 

 the muscle and mesenchyme cells form a solid mass; in the anterior quarter the chorda cells project 

 freely over the dorsal surface and the neural plate is partially infolded and contains three sense spots. 



Fig. 67. Right anterior and left posterior (diagonal) quarter embryos, dorsal view; spurted in 

 4-cell stage, fixed 22 hours later. 



Fig. 68. Left anterior and right posterior (diagonal) quarter embryos, dorsal view; spurted in 

 4-cell stage, fixed 22 hours later. In this and the preceding figure the chorda cells (Ch.), neural plate 

 (n. p.) and sense spots are found only in the anterior quarters; the muscle, mesenchyme and caudal 

 endoderm cells, only in the posterior quarters. 



Figs. 69, 70. Right anterior quarter embryos, dorsal side above; spurted in 4-cell stage, fixed 12 

 hours later. These embryos show free chorda cells, neural plate and sense spots, but not a trace of 

 muscle cells. 



