58 EMBRYOLOGY OF THE LOWER VERTEBRATES CH. 



itself becomes nipped off from the remainder of the archenteron 

 (Fig. 34, C). 



The original archenteron is now replaced by a main portion, the 



ect 



ent. 



if. Transverse sections through embryos of /,7//W",s-//v/< to illuMniU- the origin of 

 the mesocliTin. 



A, Ktegf 12 ; H and C, hta^c ] J. ect, ectoderm ; cml, riiiloilcnii ; nt, cnti'iic cavity ; nn-s. 



N, iii.to<-hurl;il i inlirncnt . 



enteron, t.h; \\jll <!' whir.h the definitive endoderm will 



ally IM-C.OIIU- 1:1 H- liniiiM- c] lit I id in in of lln' ulinn-iilary c;inal, ami, lyiiiLC 

 dorsal to this on , Bfl ofddscd sacs, <j- j.ract ically solid 



