154 G Canadian Arctic Expedition, W13-191S 



Plate XXM. 



Fig. 1. Tcalidp.iis slrila Vcrrill. Vertical section of the sphincter muscle and a tentacle of a 

 Hudson bay specimen; x 10. 



2. The same. Sphincter muscle more enlarged. 



3. The same. Part of a rather thick transverse section showing a mesentery of the third 



cycle (III) and a pair of those of the fourth and fifth cj'cles (IV, Vj covered with 

 gonads, densely crowded; g, ectoderm; h, mesoglam; e, circular muscles; i, endo- 

 dcrm; x 18. 



4. The same. Part of a transverse section showing two imperfect mesenteries deprived of 



gonads. Lettering as in fig. 3; x 25. 



5. The same. Longitudinal section of the coliuun wall, showing branched lamellse of the 



circular muscles, etc.; x 10. 

 5a. The same. More enlarged; g, ectoderm; h, mesogloea; i, endoderm; c, circular muscle 



lamella;; x 18. 

 G. Surface view of some of the suckers on the middle of the column; x 18. 

 6a. One of the suckers more enlarged; x 30. 



7. Vriinna crassicornis (Ehr.) Section of the sphincter muscle, -\fter Hargitt. 



8. Bicidiopsis arctica Verrill. Type. Part of a thick transverse section made near the 



lower part of the stomodaeum (P.), showing a perfect mesentery (i) and a pair of 

 the imperfect ones deprived of gonads. Lettering as in fig. 3. From a Hudson 

 bay specimen. 



9. Edwardsiella sipunculoides (Stimpson). A diagrammatical section near the disk 



showing the arrangement of the rudimentary mesenteries ami bases of the tenta- 

 cles; d, d, directives. After Torrey, from an Alaskan specimen. 



All the figures, except 7 and 9, were made by the author from rather thick sections, mounted 

 in glycerine-jelly, to avoid more shrinkage. 



