No. 2.] DEVELOPMENT OF THE HUMAN COELOM. 437 
the lesser peritoneal cavity.1_ Further aboralwards the cavities 
become symmetrical again (Figs. 37, 38), and then unite 
along the ventral median line, as shown in Fig. 39. The ven- 
tral mesentery shown in Fig. 38 does not extend more than a 
section or two beyond the liver, and is separated by a marked 
g 
MASS 

Fics. 37-39. — Sections through Embryo No. II. A, aorta; wc, cardinal vein; 0, omphalomesenteric 
vein ; 4, pancreas ; 2, intestine ; 4, bile duct; Z, liver; Z, heart ; #, umbilical vein ; 7, mesentery ; 
w 4, Wolffian body ; @ZZ, allantois. 
opening from the stem of the umbilical vesicle in this embryo, 
as is shown in Fig. 30, O (see also No. XII, Fig. 16, O). On 
the aboral side of the umbilical cord the peritoneal cavities of 
the two sides unite in both embryos again, marked O! in both 
figures. 
Development of Body Cavity in the Chick.— The body 
cavity of the chick has been carefully studied by Budge,? who 
followed its course by means of injection. With a fine hypo- 
dermic syringe he filled the spaces forming the coelom in the 
order of their appearance, thus showing their extent in vari- 
ous embryos. The splanchnopleure, according to Budge, may 
be split into two layers, one dorsal or lymphatic and the other 
ventral or vascular. Drasch’s® recent description of the early 
1 Mall: Journ. of Morph., vol. V. 
2 Budge: His’s Archiv, 1880 and 1887. 
3 Drasch: Anatom. Anz., Bd. 9. 
