152 G Canadian Arctic Expedition, 1913-1918 



Plate XX^'. 



Fig. 1. Bicidiopsis ardica Verrill. Type. Transverse thick glycerine section across near the 



upper part of the cohimn, showing 12 perfect and eight imperfect mesenteries; 



d, sulcar; d', sulcular directives and siphonoghlyphs; 1, 1, gonads on imperfect 



mesenteries; o, stomodsEum. Schematic, in part, 

 la. The same. One of the perfect mesenteries more enlarged, 

 lb. The same. Conehula and siphonoglyph much enlarged. 

 Ic The same. Distal part of a tentacle; much enlarged. 



Id, a, b. .Sections of two tentacles compressed into angular forms by crowding. 

 le. The same. Longitudinal section, in the region of the sphincter muscle (e); much 



enlarged . 

 If. The same. Portion of a mesenterial filament partly imcoiled. Ig. Another portion 



more enlai'ged; Ih, trifid portion, 

 li. The same; transverse section at base of the stomodaeum, showing the bases of the 



directive mesenteries (d) ; g, ectoderm; h, mesogloea; h', lines of circular muscles. 

 Ij. The same; terminal pore and ends of mesenteries seen from inside; enlarged. 

 Ik. Section of aboral end and pore expanded; m, mesenterj-; p, pore. 



2. Metridiiim dianOms (Ellis). A large living specimen with some acontia emitted; 



from Massachusetts Bay; n, n, acontia; about f natural size. 



3. Stphonactinm parasilica. Two of the mesenteries in tran.?verse section. After ]\Ic!MuT- 



rich, with some changes. 



Figm-es 1-lk, were made from rather thick sections motmted in glycerine-jelly and therefore 

 differ from hardened sections in Canada balsam. By the a\ithor. Fig. 2, after J. H. Emer- 

 ton, with some changes. 



