GEROULD. — Caudina. 
Fig. 80. 
Fig. 81. 
Fig. 82. 
Fig. 83. 
Fig. 84. 
Fig. 85. 
Fig. 86. 
Fig. 87. 
PLATE 6. 
ABBREVIATIONS. 
Radial water canal. mu. lg. Longitudinal muscle fi- 
Follicular cell. bers of body-wall. 
Radial epineural canal. mu. lg.! Longitudinal muscle fi- 
External epithelium of bers of rudimentary 
Polian vesicle. ambulacral foot. 
.oa. External epithelium of mu. tr. Transverse muscles of 
the ovary. Nn. Nerve. [ body-wall. 
Internal epithelium par. oa. Wall of the ovary. 
Hyponeural canal. tis.cov't. Connective tissue. 
Lacunar blood vessel of vt. ex. External layer of yolk. 
Micropyle. [the ovary. Bis Os Internal layer of yolk. 
Circular muscle fibers. gare Zona radiata. 
Cross section of the stone canal.  X 12. 
Section of the madreporic body, nearly perpendicular to its flat sur- 
faces. 37. 
Longitudinal section through the wall of the Polian vesicle. 555. 
Cross section through the wall of the circular water canal. XX 53 
Longitudinal section through a tentacular canal and upper part of 
radial plate, showing the valve of the tentacle. X 280. 
Diagrammatic radial section through a tentacle showing the circula- 
tion of fluid in it. 
Cross section through the posterior end of a radial water tube and its 
lateral vessels (rudimentary ambulacral feet) along the line AB of 
Fig. 80.  X 280. 
Graphic reconstruction of the terminal tentacle (the anal papilla) and 
the two rudimentary ambulacral feet. Scale 6% p to 1 mm., or 
x 150. 
Peritoneal epithelium from the wall of the ovary. Maceration prepa- 
ration.. X 240. 
The same. Silver-nitrate preparation. X 240. 
Part of a cross section of wall of ovary ofa young individual. 720. 
Muscle fiber from the wall of the ovary. X 205. 
Follicular epithelium. Silver-nitrate. x 240. 
Part of cross section of wall of ovary of Cucumaria frondosa. X 240. 
Young ovum. X 235. 
Figs. 88,89. Slightly older stages in the growth of the ovum. X 235. 
Fig. 90. 
Fig. 91. 
Ovum showing deep staining of a superficial layer, preparatory to 
formation, of a zonaradiata. 235. 
Ovum showing two layers of yolk separated by intravitelline mem- 
brane. X 236. 
Surface view of interior of ovary showing a well-grown ovum in posi- 
tion and the micropyle projected on the germinative vesicle. X 226. 
Section of a nearly full-grown ovum. Fol’s chromic-osmic-acetic 
mixture. Ehrlich’s haematoxylin and eosin. X 255. 
