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C.—THE BODY-CAVITY AND ITS VISCERA. 
We propose describing under this section the alimen- 
tary canal, the digestive and ductless glands and the renal 
organs, leaving the reproductive organs to be described 
in Section G. 
1.—Tus Cantomic Spaczs. 
The derivatives of the embryonic ccelom are (1) the 
body cavity, (2) the pericardium, (5) the cavities of the 
ovaries (in the female), and (4) the cavity of the ureters. 
The body cavity is bounded dorsally by the kidney, which 
les underneath vertebra 2 to 14, anteriorly by the pos- 
terior fibrous wall of the pericardium, the lower portions 
of the clavicles, the innominate bones and the muscles of 
both limb girdles, and posteriorly by the Ist haemal spine 
(HS. 1, fig. 21) and the 1st axonost (1. Az.). It contracts 
ventrally, so that only a small region surrounding the 
anus is bounded by the ventral body wall. The lateral 
body walls are strongly muscular, and the parietal peri- 
toneum is deeply pigmented. ‘There is no posterior exten- 
sion of the body cavity on either side, such as occurs in 
the Sole, and is stated by Kyle to exist also in the Plaice. 
The nature of the cavities of the ovaries and renal 
organs is best considered with the description of those 
organs. 
2.—THE ALIMENTARY CANAL AND ITS GLANDS. 
The alimentary canal may be conveniently divided 
into the following regions: cesophagus, stomach, duo- 
denum, intestine and rectum. (isophagus and stomach 
are distinguished from each other and from the rest 
of the alimentary canal by the differentiation of the 
mucous membrane. ‘The duodenum is the proximal 
