560 



NOTnC'lfORD 



plate ha. become separated from the outer ectoderm. 

 In the mid-dorsal line a thickening of the endoderm 

 (.//) soon becomes constricted off to form the notochord 



Y, 



hi: 



l''i(.. 141, -Four stages in tlie Je\'tlopmtint of the nntorhni-t!, iier\oiis s>,,teni, and 



mesodenn iif Ant/>/i/o.vi/s. 



ak. ectoderm ; ch notochord ; dh. cavity of aicheiiternii ; ///>. ridge- of ectodeim 



^luuillg over mcdiillar\- plate ; //■. endoderm ; ///, ccu-lome ; /;/^. cctlomic poucli ; 



////■I. ])arictal layer of mesoderm ; )iik'-. \i-^ceral layer; ;///. medullary plate ', '/. 



ijK-diillary cortl; «.s". proto\ ct teVira. (From Kor-^chell antl Heider, after Hatschek.) 



(pp. 203, 404 and 425), and on t-ilhcr side of this 

 a scries of hollow endodcrmic pouches arise, arranged 

 nietamerically (Figs. 143, ////■, and 144, ns^ mk). The 



