63 



C— THK 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 (j. 



1. — The C(elomic Spaces. 



The derivatives of the embryonic coeloni are (1) the 

 body cavity, (2) the pericardium, (-3) the cavities of the 

 ovaries (in the female), and (4) the cavity of the ureters. 

 The body cavity is bounded dorsally by the kidney, Avhich 

 lies 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 1st haemal spine 

 {H.S. 1, fig. 21) and the 1st axonost (1. Ad'.). 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. Ihere is no posterior exten- 

 sion of the bodv 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 (Ianal and its Glands. 



The alimentary canal may be conveniently divided 

 into the following regions : (esophagus, stomach, duo- 

 denum, intestine and rectum. (Esophagus 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 



