Fig. 119. — DcvcloiMiicnt of tlio Frog;. .\-F, cleavage; 0, overgrowth of 

 ectoderm; II, I, es(a1)lLshnicnt of gorni-la>'ers; J, 1\, assumiition of tadpole-form 

 and estal)Ushment of nervous sysleni, notochord and enteric canal (archenteron); 

 L, newly-hatched tadpole. />/. coi/, blastoco'lo; lilp. hip', blastopore; hr' . hi", 

 cutaneous gills; hr. cI, brani'hial arches; c, eye; crl, ectoderm; ciul, endoderm; 

 evr, entcroti;/, hr, fore-lir:un; h. hr, hind-lirain; iii. hr, mid-brain; iiul.f, medullary 

 fold; iitil.ijr, m(Mlu]l;u-\' gi'o(i\'e; iius, mcsiidcrm; iiuj, megameres; »ii, micromercs; 

 «(■//, notochord; ii.c.r, ucurentcric canal; pnliii, i)ro(^todaHUn; /if;/, pituitary in- 

 vaginalion; rrl, cniuincnccnicnt of rccliun; .>;/,■, sucker; sp.cil, spinal cord; sidin, 

 stomodaaun; /, tail; ///.', yolk cells; i//.-. /)/, yolk plug. (From Parker and Haswell, 

 after Zicgler and Marshall.) 



206 



