Fig. 13 X'entral view of inodol of nipsodenn, iiicscncliymo and v:i.scul:ii- nnlages 

 of an embryo of twelve soinilps. /. Dorsal aorta:.?, hypectodennal nie.sencliyme; 

 l^, aiinidcy.sts of uiiiliilical vein: n, rocloinic anfiie. 



(iS 



