No. 2.] DEVELOPMENT OF THE HUMAN COELOM. 431 
Fig. 30, O, but a new process has already taken place to com- 
plicate matters. 
In embryo XII there is just a beginning of an umbilical 
vein in the membrana reuniens. In Kollman’s embryo the 
vein is more marked.!_ The vein extends out into the somato- 
pleure, far away from either the intestine or the median line. 
This same position is again shown in His’s embryos BB. and 
Lr on Plate IX in his A¢das. The left umbilical vein becomes 

Fic. 29. — Embryo No. II Attached to the Chorion. Enlarged 5 times. Just half of the Ovum is 
shown. O », otic vesicle ; VU Z, upper extremity ; Z Z, lower extremity; JV, nose; J, //, ///, 
branchial arches. 
the more prominent, and as the body wall is developed more 
and more it moves around towards the ventral median line. 
This movement takes place in common with the movement of 
the amnion over the body from left to right, as shown in Fig. 
28. In embryo No. II, however, the liver has nearly reached 
the umbilicus, and the vein has almost moved around to the 
1 Kollman: His’s Archiv, 1891, Plate III, Figs. 2, 3, 4. V. umbil. 
