PSEUDOCOELOMATE AND MINOR EUCOELOMATE PHYLA 



the coelomic fluid probably occurs, and in the absence of a vascular system 

 the coelomic fluid presumably serves as a circulatory medium. Excretory 

 organs are lacking, although cells of the stomach epithelium appear to ac- 

 cumulate waste products in the form of brown granules. In older individuals 

 these brown concretions are conspicuous, and eventually the entire body of 

 the organism, with the exception of the cuticular sheath, progressively degen- 

 erates into a so-called "brown body." The significance of this process is not 

 entirely clear. 



The nervous system of the zooid is simple, consisting of a single ganglion in 

 the region between mouth and anus, with fibers innervating sensory cells 

 and muscle bands in the tentacles as well as other muscles in all parts of the 

 body. 



The coelom, probably developed by a schizocoelous process (p. 368), is 

 lined by visceral and parietal peritoneum connected by a mesentery (funiculus) 



Fig. 12.10. General structure of an encrusting ectoproct, based on Membrampora. A, individual 

 with lophophore extended; B, with lophophore retracted. In both diagrams the individual is 

 represented as thou8;h sectioned alons; the midsas;ittal plane. The peritoneal lining of the coelom, 

 and the remnants of mesenteries and septa, are indicated by broken lines. Note the position of 

 the anus in relation to the circlet of tentacles about the mouth. C, surface view of a portion 

 of a colony of Membrampora tuberculata, with all individuals retracted. Note the crescentic 

 operculum at the anterior end of each individual. {A and /?, redrawn from C. Cori in VV. 

 Kijkenthal and T. Krumbach, 1938. Handbuch rler ^oolo^ie: C, photoa;raph bv Geore;e Lower.) 



359 



