Fig, 137. 
Fic. 138 
Fig. 139 
Fig. 140 
Figo. 141 
Fig. 142 
59 
05 
. 148 
144 
145 
146 
147 
08° 3° de" dS" 
bay bef fy 
ar 
DR. KE. B. WILSON ON THE DEVELOPMENT OF RENILLA. 813 
Longitudinal section through a seventy-five-hours’ larva. Cisophagus still 
closed. 140. 
Similar section through a slightly later stage (100 hours). x 140. 
A similar section of a sixty-two-hours’ embryo; the cesophagus has just 
broken through. X 140. 
Longitudinal section of seventy-five-hours’ larva. Mouth fully formed, but 
“cesophageal plug” (pl.) still adhering to the edge of one of the septa. 
«140: 
Sixty-hours’ larva. Mouth breaking through bottom of stomodzeum, x 140, 
Transverse section through anterior part of forty-eight-hours’ larva. 315, 
PLATE 60. 
Transverse section from same specimen further back at the level of lower 
end of cesophagus. X 315. 
Transverse section through anterior part of a four-days’ larva. 315. 
From same larva at lower end of cesophagus. 315. 
Transverse section of four-days’ larva posterior to cesophagus. X 350. 
Part of a transverse section through a forty-eight-hours’ larva showing a 
septum and general histology. Xx 880. 
Fig. 147%. Portien of ectoderm from last. x 880. 
Fic. 148 
Fig. 149 
PLATE 61. 
Section through lateral attachment of peduncular septum to body-wall. 
Forty-eight hours. Xx 350. 
Section through radial septum and part of body-wall. Forty-eight hours. 
X 350. 
Longitudinal section through posterior part of body of a forty-hours’ larva to 
show formation of peduncular septum. 135. 
. Transverse section through posterior part of a forty-eight-hours’ larva showing 
peduncular septum. X 315. 
Transverse section through the free-edge of the peduncular septum. Forty- 
eight hours. xX 180. 
Part of longitudinal section through peduncular septum, highly magnified, 
to show axial cells. X 350. 
Transverse section in front of peduncular septum. Forty-eight hours. 
xX 315. 
Longitudinal section just above peduncular septum. X 220. 
Transverse section through peduncular septum at its attachment to the 
body-wall. Forty-five hours. 
MDCCCLXXXIII. 2M 
