PLATE VIII. 



CLADOCORA ARBUSCULA (Lesueur). 



Fig. 59. — Transverse section through a part of tlie discal region of a retracted polyp, with two attached mesenteries 

 (directives) and the entoccrlic septal invagination {sep. inr.). The skeletogenic ectoderm {cat.) 

 lining the inner calicinal wall is a very distinct layer at this level, and also along the innermost 

 part of the invagination, l)ut is absent from the lateral surfaces. X 320. 



Fig. 60. — Transverse section through the elevated peristome of a bud polyi>. Five pairs of complete protocnemes 

 are present; the incomplete sixth pair is represented below, along with the six pairs of first- 

 cycle metacnemes. The reflected stomodwal ectoderm (r. eel.) is seen on the left side (cf., fig. 51). 

 X 120. 



Fig. 61. — Transverse section of a butl polyp with eight complete mesenteries, which at the level represented are 

 filamentiferous. Two unilateral pairs of metacnemes (A,A) have appeared on the ventral, sulcar, or 

 outer border. X TO. 



Fig. 62. — Transverse section of a pentameral bud [lolyp, with the metacnemic pairs showing successive stages ip 

 development from the lower (abaxial) to the upper (axial) aspect. X 70. 



Fig. 63. — Section of tlie upper skeletotrophie layer, where the calicoblast layer is well developed. Desmoidal 

 processes are indicated by the striated bodies, but in the section are free from the mesoglica. X 320. 



ORBICELLA ANNULARIS (p:ilis c'c Solauder). 



Fig. 64. — Radial section througli the column wall, perforated for the passage of a mesenterial filament and the 

 mesentery to which it is attached. (See p. 475.) X 300. 



Fig. 65. — Radial section through the infolded edge of the column wall of a retracted polyp. The endodermal 

 musculature forms a weakly diffuse endodermal sphincter muscle; pigment granules occur in groups in 

 the ectoderm of the outer part of the wall. X 300. 



Fig. 66. — Section through the skeletotro]ihic tissue lining the upper part of the theca. The edge of the liroad calico- 

 blast layer (eel.) is irregularly jagged. X 400. 

 614 



