814 DR. E. B. WILSON ON THE DEVELOPMENT OF RENILLA. 
PLATE 62. 
Figs. 157, 158, 159. Longitudinal sections through 100-hours’ larvee showing con- 
tinuity of stomodzal ectoderm with the mesenterial filaments. Xx 140. 
Figs. 160, 161. Surface views of four-days’ larvee to show muscular fibres. x 880. 
Fig. 162. Transverse section through the dorsal median tract of longitudinal muscles. 
Four days. X 880. 
Fig. 163. Transverse section through ventral median tract of longitudinal muscles. 
X 880. 
Fig. 164. Corresponding section through a younger specimen. X 880. 
Fig. 165. Transverse section through septum and a septal tract of longitudinal 
muscles. x 880. 
PLATE 63. 
Fig. 166. Transverse section through septal tract below the septum. 
°. 167. Transverse section through body-wall and peduncular septum to show 
longitudinal muscles in the ventral side of the latter. 
Fig. 168. Part of longitudinal section through the body-wall showing the circular 
muscles. xX 880. 
Fig. 169: Transverse section through body-wall showing circular muscles in longitudinal 
section. xX 880. 
Fig. 170. Various forms of myoblasts from the entoderm. 700. 
Fig. 171. Cells from the deeper layers of the ectoderm with spicules developing in 
their interior. 700. 
Fig. 172. Entoderm cells with spicules in course of formation. 700. 
PLATE 64. 
Fig. 173. Section through a four-days’ larva passing through one of the buds (p!.). 
<allos 
Fig. 174. Similar section passing through bud at p!.; a, lateral forward extension of 
peduncular septum. 315. 
Fig. 175. Transverse section through four-days’ larva passing through both buds. 
x 315. 
Fig. 176. Ventral view of four-and-a-half-days’ young polyp. X56. 
Fig. 177. The same specimen one day later from the left side. 56. 
PLATE 65. 
Fig. 178. Young polyp of about nine days from right side. x 30. 
Fig. 178%. Tentacle. x 45. 
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