30 THK NAUTILUS. 



Figure G. Diagrammatic cross section of Calyculina to show 

 opening of genital ducts. 



Figure 7. Frontal section of neutral part of inner gill, show- 

 ing fusion of the two lamellae. Calyculina. 

 I L — Inner lamella Ifj — Interfilamentary junc- 



L — Outer lamella tions 



Bis — Blood space Cl — Cro.'=«s threads 



Figure 9. Part of inner wall of the brood pouch of Cyclae. 

 (Copied from Poyarkoflf). 



L — Leucocyte lodged at base of cells 

 F — Leucocyte just entering wall of pouch 

 A — Leucocyte beginning to divide 

 iV — Polynucleate cell 



Plate VI. Figure 10. Shell of Spaerium simile showing 

 growth lines. 



U — Umbo i, 2, 3, 4, — Growth lines 



Figure IL Diagrammatic reconstruction of a portion of the 

 inner gill of Calyculina, showing the relation of brood pouches 

 to gill filaments. 



/ L — Inner lamella Em — Embryo 



L — Outer lamella I W — Inner wall of brood 



C/ Ch — Cloacal chamber pouch 



If J — Interfilamentary junc- W — Outer w^all of brood 



tion pouch 



G F — Gill filament Bis — Blood space 



