B 



mi 



bl.cofil 



2/kpl 



m.l/r 





pcdm V ■ ■>A 



ent 



Fig. 930.— Development of the Frog. A— K, ^se^lll>JnTatioll ; G, overgrowth of ectoderm ; H, I, 

 establishment of germinal layers ; J, K, assumption of tadpole-forjn and establishment of 

 nervous system, notochord, and enteric canal ; L, newly-liatched tadpole. bl.c(d. blastoccele ; 

 blp. Up'. blastop(jre ; bA. br". gills ; br. li. branchial arches ; e. eye ; ect. ectoderm ; ciid. 

 endoderm ; ent. enteron ; /. hr. fore-brain ; h. br. hind-brain ; m. br. mid-brain ; md. f. 

 medullary fold ; md. (jr. medullary gi-oove ; iiuk. mesoderm ; mil. megameres ; mi. micromeres ; 

 iich. notochord ; n. e. c. neurenteric canal ; pcdm. proctodasum ; pty. pituitary invagina- 

 tion ; ret. commencement of rectum ; sk: sucker ; sp. rd. spinal cord' ; st.dai. stomodasum ; 

 t. tail ; -Ilk. yolk cells ; vk: pi. yolk plug. (A— D, F— H, and J from Zieglcr's models ; 

 E, I, K, and L after Marshall.) 



