10 AKT. 4.— EKITARO NOM UK A : 



1). The mouth lies ventrally at the beginning of the first 

 segment. The buccal cavity is flattened dor so -ventrally and ends 

 in segment ^ II, becoming smaller and ±- shaped. The wall con- 

 sists of 5 layers corresponding to those of the body wall. The 

 cuticle is as already mentioned a direct continuation of the cuticular 

 layer of the body wall, but there are no pore- canals in it. The 

 hypodermis does not contain gland cells but is otherwise similar 

 in structure. The circular and longitudinal muscles are very 

 weakly developed, and the peritoneum is also changed into a 

 solid tissue. 



2). The pharynx is the direct posterior continuation of the 

 buccal cavity ; it begins in segment J II and reaches to the end 

 of segment III. The inner cavity is very spacious, except at the 

 anterior part, where it is very narrow, and the ± -shape of the 

 mouth cavity passes over into an irregularly penta-radiate form 

 by foldings of the pharyngeal wall. About the middle of the 

 pharynx, where the cavity is broadest, the lumen again becomes 

 X-shaped. At the posterior part the median inlet disappears more . 

 or less suddenly and passes over into the dorso-ventrally flatten- 

 ed, but laterally extended oesophagus. In completely narcotised 

 specimens the median inlet is not very deep and the entire cavity 

 has somewhat the form of a semicircle in cross-section. 



The wall of the pharynx appears to consist of two layers. 

 The inner or endodermal layer consists of exceedingly long, 

 cylindrical, ciliated cells ; the cytoplasm is somewhat granulated 

 and an exceedingly elongated nucleus lies at the middle or in the 

 proximal half. The cilia are stouter on the dorsal than on the 

 ventral side. The outer layer is made up of several elements, 

 viz. exceedingly fine blood capillaries, pretty well developed 

 circular and very weakly developed longitudinal muscle fibres, 

 and connective tissue between them. Besides these there are 

 muscle fibres running between the pharyngeal and the body wall. 



On the dorsal side of the pharynx and attached to its wall 

 there are certain cells with dense cytoplasm, which are not 

 chloragogues. These cells, which are pharyngeal glands, are also 

 present in L. willeyi, as will be seen later. 



