SIBOGLINUM SUBLIGATUM 283 



The metameric section of the metasoma is very long and the moderately 

 broad dorsal ciliated band begins at its front border. The plaqueless meta- 

 meric papillae are well differentiated. They are more or less rounded, 

 similar in size and closely pressed together (Fig. AA133Z)). A single pyri- 

 form gland can be made out inside each papilla, and on the surface of the 

 papilla a small clear ring represents the rosette of gland cells surrounding 

 the external pore of the pyriform gland (Fig. АА133Д D). A tract of 

 glandular epidermis, whitish in reflected and opaque in transmitted light, 

 extends along the bases of the papillae on the external side of each row 

 (Fig. АА133у4, С, D). Towards the hind end of the metameric region the 

 papillae become considerably larger and sparser. In general the number of 

 metameric papillae lies between 75 and 105 pairs. 



The nonmetameric part of the trunk is several times longer than the 

 metameric section and characterized by the unusually strong development 

 of the granular gland cells of the epidermis. In reflected light this part 

 stands out because of its intense whiteness, which in turn depends on the 

 granular secretion of the glands. The lateral glandular tracts of the metameric 

 region extend, gradually broadening out, far backwards along the whole or 

 almost the whole length of the pre-annular region. The glandular epithelium 

 in places covers almost the whole surface of the trunk, which lacks gland 

 cells only along narrow mid-dorsal and mid-ventral strips (Fig. ВВ133у4). 



There is no definite zone of thickened papillae, but three to five large 

 conical papillae are present immediately in front of the girdles. They do not 

 bear plaques and are arranged in a single row along the ventral side close to 

 each other (Figs. ВВ133Я, СС133Л). 



In all the specimens which have been investigated I have found two 

 girdles. Both are broken by a wide gap on the ventral side only (Figs. BB1335, 

 CC133v4). Behind the girdles there is always a conical ventral papilla 

 which likewise bears no plaque (Figs. BB1335, СС133Л). The yellowish 

 toothed platelets are arranged on the surface of the more or less broad 

 protuberant ridges of the girdles in two or sometimes in three or four 



Fig. AA133. Siboglinum subligatum: A - fore-part of the body in ventral view; В - protosoma from 

 the dorsal side; С - region where the meso- and metasoma meet, in dorsal view; D - fore-part of 

 the body from the left side. 



ag- ventral glandular region of the mesosoma; с - cephalic lobe; со - dorsal ciliated band; 

 /-bridle; ms - mesosoma ; mts - metasoma ; pa - papillae ; ps - protosoma ; r- rosette of gland 

 cells around the pore of a pyriform gland ; s 1 - groove between the protosoma and mesosoma ; 

 s 2 - groove between the mesosoma and metasoma; sv - ventral sulcus; / - tentacle; tg - glandular 

 ribbon of the mesosoma; //- lateral glandular tract of the metasoma. 



