No. 2.] DEVELOPMENT OF THE HUMAN COELOM. 433 
always slightly to the left of the median line, and is in direct 
connection with the septum transversum (Fig. 30, O and S 7).’ 
Coelom of Embryo No. II. — After the body cavity is begin- 
ning to separate from the extraembryonic coelom, the next im- 
portant stage is the one after the separation is complete, as from 
now on the adult body cavities are formed by a simple division 
and expansion of the cavities already within the body. This 
stage is represented in em- 
bryos XVIII, II, and IV. 
All of these embryos are 
nearly of the same size, 
the successive stages being 
in the order they are given. 
No. XVIII is somewhat 
distorted in the middle of 
the body, while No. IV is 
slightly macerated. No. II 
is a perfect specimen, and 
has been already described 
by me several years ago.1 
I shall confine my descrip- 
tion of it to the body cavity. 
The external form of the 
embryo within the ovum is 
given in Fig. 29. The Fie. 31.—Cast of the Body Cavity of Embryo No. 
Heagon ef the\ umbilical, 7 BUA ee 
vesicle, as well as the ex- entery; W B, position of Wolffian body; P, 
FeO Het nian ancl the pericardial cavity ; Z, coelom over liver. 
relation of the umbilical vesicle and amnion to the chorion, are 
all given. The umbilical cord is large and lies on the left side 
of the body, while in most embryos already published it is upon 
the right side. The cord is short, and midway between the 
embryo and its attachment to the chorion it shows a decided 
enlargement. The umbilical vesicle is large, measuring 5 X 7 
mm., and is located between the head end of the embryo and 
the chorion. 
The amnion has not grown very much, still leaving a great 

1 Mall: Journ. of Morph., vol. V. 
