1 50 MCMURRICH. 



EXPLANATION OY PLAT?:S VI. .\ND VII. 



Plate VI. 



Figs. I and 2. Cerianthus Americanus, Ag. — Fig. 1, natural size; Fig. 2, reduced 

 •ne-third. 



Plate VII. 



Fig. I. View of specimen laid open by a longitudinal incision passing near the 

 mid-dorsal line, si = siphonoglyphe, ac = acontia, s/ = stomatodaeum, 3 = mesentery 

 of third grade. 



Fig. 2. Semi-diagrammatic, showing the relations of the mesenteries of the dif- 

 ferent grades. 3 = mesentery of third grade, 4 = mesentery of fourth grade. 



Fig. 3. Section through ventral portion of column, just above the lower end of the 

 stomatodseum, Z? = ventral directive mesenteries, i and i'= mesenteries of the first 

 grade, 2 = mesentery of the second grade, 3 and 3' = mesenteries of the third grade, 

 4, 4', 4", and 4'"= mesenteries of the fourth grade. 



Fig. 4. Section through ventral portion of column wall, about 2 mm. below Fig. 3. 



Fig. 5. Section through ventral portion of column wall, about 1.5 mm. below Fig. 4. 



Fig. 6. Portion of tangential section of disc, cm = circular muscles, mg= mes- 

 ogloea, /m = longitudinal muscles, « = nerve layer, pm = process of mesogloea. (Zeiss 

 obj. J, oc. 2.) 



Fig. 7. Transverse section of stomatodceum (Zeiss obj. J, oc. 2). 



Fig. 8. Section of mesentery in the angle formed by the meeting of the disc and 

 column wall (Zeiss obj. J, oc. 2). 



Fig. 9. Transverse section of mesentery in the gonophoric region, with ovum 

 (Zeiss obj. D, oc. 2). 



Fig. 10. Portion of Fig. 9, more highly magnified to show the network. fn^ = 

 mesogloea, /= food particle (?). (Zeiss obj. J, oc. 2.) 



