atdm. 



FIG. 64. Development of the Frog. 



A F segmentation ; G, overgrowth of ectoderm; H, I, establishment of germinal 

 layers ; J, K, assumption of tadpole-form and establishment of nervous system, 

 notoch'ord, and enteric canal : L, newly hatched tadpole. ( x 10.) 



6*. cal. segmentation cavity ; blp, blp', blastopore : 6fi, bf\ gills ; br. a. branchu 



notochord ; n. e. c. neurentenc canal : pcdm. proctodaeum ; ply. invagina- 

 tion of ectoderm which will form the pituitary bodv ; ret. rudiment of rectum ; 

 s* ucker s/>. cd. spinal cord ; stihn. stomodaeum ; /. tail : yk. yolk-cells ; 

 vh pi. yolk-plug which fills the blastopore. (From Parker and Haswell 3 

 'Zoology. A D, F H, and J from Ziegler's models, E, I, K, and L 



after Marshall.) 



