PLATE XII (continued). 
Fig. 
9.—Inner membrane lining the natatory sac of LZ. octoradiata. Xx 260 
diameters. 
10.—Transverse section of the stem of Z. campanulata: a, outer, 7, inner, 
cellular coat ; z, transversely striated intermediate substance ; 2, the 
four internal ridges. 
11.—Longitudinal section of the same, carried in the direction a B of the 
foregoing figure ; 4, ceecal hollow in the pedal disc. Other letters as 
before. 
12.—Longitudinal section through the foot, in order to display the cecal 
hollow more plainly. Letters as before. 
13.—Transverse section through the stem of L. octoradiata. 
h. The four longitudinal channels which replace the central cavity. 
14,.—Glandular inversion of the wall of the natatory sac (s) of Z. campanu- 
lata, indicated at x in fig. 4; x, orifice by which the thread-cells can 
be expressed. 
15.—Thread cells: a, with extended filaments still enclosed in the parent 
cell. x 260 diameters. 
16.—Internal oral tentacles of L. campanulata. 
17.—Transverse section of the same, showing the extent of the glandular, 
thickened part of its wall. 
18.—Zoosperms of L. octoradiata. 
