374 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Plate XI. 
Fig. 39. JBunodosoma spherulata. Transverse section of a portion of the column-wall some distance 
below the stomodseal region, with a mesentery attached showing the circumscribed 
retractor muscle, the parieto-basilar muscle, and the simple filament. 
Fig. 40. Transverse section of a polyp toward the termination of the stomodseum, indicating the 
sequence in which the pairs of the second order of mesenteries become free from the 
stomodseum. 
Fig. 41. Aiptasia annulate. Oblique section through an expanded tentacle, showing the ectodermal 
thickenings (batteries of nematoblasts) and the distribution of the zooxanthellse within 
restricted swollen regions of the endoderm. 
Fig. 42. Vertical section through the middle region of the column-wall. 
Plate XII. 
Fig. 43. Aiptasia annulata. Transverse section through the stomodseal region of a polyp. Four cycles 
of mesenteries are present, but only four bilateral pairs (Edwardsian mesenteries) are com- 
plete; the fifth and sixth developmental pairs are incomplete. All the incomplete mesen- 
teries are gonad bearing. 
Fig. 44. Transverse section through a trilobed mesenterial filament. The intermediate streak {wit. st.) 
between the glandular streak and the ciliated band is of considerable extent and contains 
many zooxanthellse. 
Fig. 45. Calliactis tricolor. Vertical section through the upper part of the column-wall, showing the 
mesoglceal sphincter muscle. 
Fig. 46. Vertical section through a portion of the basal wall, showing the weak basilar muscle on each 
side of a mesentery. 
