342 ARTHUR WILLEY. 
From living specimen. Tentacles retracted. ¢.0. Opening of tentacle 
sheath. 
Fic. 4.—Sketch of Ctenoplana as it may be seen when attached to the 
surface-film of water. In the centre is seen the mouth. The two end-lobes 
of the central gastric system show up white. 
Fie. 5.—C. Korotneffi. Section parallel to stomachal plane (i.e. trans- 
verse to tentacle axis) to show the origin of the genital cecum, &c. The 
section is somewhat oblique. cé/. Ciliated epithelium of ventral surface. 
ce. Genital cecum. ch. Chloragogenous cells. c¢.p. Ctenophoral plate, re- 
tracted. d.e. Dorsal spongy vacuolar non-ciliated epithelium, with mucous 
granules at external surface. These cells would seem to be comparable to 
the so-called “ Glanzzellen” of Ctenophora. ext. Colenteron. ep. Diges- 
tive epithelium, nuclei placed near free end of cells. These are clear faintly 
staining cells with indistinct cell outlines, and with a sharply defined non-ciliated 
free margin. gez. Genital proliferation on the wall of the genital cecum. 
g.p. Gastric proliferation. mes. Mesenchymatous tissue. ¢.0. Opening of 
tentacle sheath. ¢.s. Tentacle sheath with its ciliated epithelium; the 
tentacle itself is retracted further back. v.e. Non-ciliated glandular epithe- 
lium of the ventral surface. 
Fic. 6.—The same. Succeeding section to preceding through gonad to 
show the conversion of the genital cecum into a canal. ce. Genital cecum. 
s. Genital proliferation broken up into polygonal groups of sperm mother- 
cells. 
Fie. 7.—C. Korotneffi. Section through the region of the gonad of 
another individual to show the testis full of mature spermatozoa and the 
opening of the genital duct. d. Tangential section of portion of duct. d.e. 
Dorsal epithelium. g.o. Genitalaperture. ¢.p. Tunica propria with flattened 
nuclei in its walls. 
Fig. 8.—The same. Succeeding section to preceding to show junction of 
genital duct with tunica propria. 
Fic. 9.—Section through a gonad of same individual as that from which 
fig. 5 was taken, to show subdivision of the testis. c@. Genital cecum. 
d. Genital duct. s'. Spermatogonia. s*. Spermatocytes. s*. Spermatidia. 
s4. Spermatozoa. ¢.p. Tunica propria. 
Fie. 10.—Section through tentacle and its sheath. c.s. Cavity of sheath. 
s. Wall of sheath composed of ciliated epithelium. ¢. Tentacle with peri- 
pheral nuclei and central muscle-fibres. In the centre of the tentacle runs a 
core of mesenchyme-cells, mes. p. Branch or pinna of the tentacle. 
Fie. 11.—Schematic figure to explain connections of the lobes of the 
central portion of the gastro-vascular system. /. Position of funnel vessel. 
