572 
H. V. WILSON 
EXPLANATION OF FIGURES 
1 Stylotella. Dermal membrane over subdermal cavity — from thick tangential 
section, cc, cells lining subdermal cavity; ep.n., epidermal nuclei; m.c, mesen- 
chyme cells; p.c, wall of pore canal; p.m., pore membrane; s.c.w., wall of sub- 
dermal cavity. X 1200 (Zeiss 2 mm., oc. 6).^ 
2 Stylotella. Dermal membrane perforated by pore canals — from thick tan- 
gential section. Pores closed. References as before. X 1200. 
3 Stylotella. Dermal membrane perforated by pore canals — from thick tan- 
gential section. Pores partially closed. References as before. X 1200. 
4 Stylotella. Dermal membrane showing osmic-silver artefacts. From thick 
tangential section. X 1200. 
5 Stylotella. An oscular lobe was cut transversely. Part of cut surface is 
shown; canals have been closed in by newly formed membrane, c/i., choanosome; 
col., collenchyma; c.w., wall of canal; cm., newly formed membrane closing in the 
canal. X 85. 
6 Stylotella. Regenerating epidermis. Exposed surface two hours after cut- 
ting. X 1200. 
7 Stylotella. Regenerating epidermis. Exposed surface five hours after cut- 
ting. X 1200. 
8 Stylotella. Regenerating epidermis. From tangential section of new dermal 
membrane that has closed in a canal. Five hours after cutting. Body of figure 
is drawn at a focus below cut surface, and shows mesenchyme cells, m.c] p.c, 
space in mesenchyme, probably representing pore canal. At a different focus the 
epidermis, p.vi., is drawn where it roofs in the space. In such a position the 
epidermis presumably forms a (closed) pore membrane. X 1200. 
9 Stylotella. Regenerating epidermis. Exposed surface twelve hours after 
cutting. Pore canals, p.c, now perforate the dermal membrane; small perfora- 
tions of the epidermis, per., occur. X 1200. 
10 Reniera. Successive stages in the closure of a pore. X 600 (Zeiss D 4). 
11 Reniera. Epidermis from an oscular tube. Walls of pore canals, p.c, 
shown at a lower focus. Pore canals partially or completely closed in by pore 
membranes, p.m. X 1200. 
12 Reniera. Successive stages in the closure of a pore. X 600. 
13 Reniera. Dermal surface. — from an oscular tube, p.c, pore canal of 
fig. 12, now closed in and contracted; a-d, cells in the mesenchyme. X 600. 
14 Reniera. Successive stages in the closure of a pore. X 600. 
15 Reniera. Successive stages in the closure of a pore. X 600. 
16 Reniera. Successive stages in the closure of a pore. X 600. 
17 Reniera. Three pores showing pseudopodial activity, at margin (a, c), or 
at margin of incomplete pore membrane (6). X 600. 
- 18 Lissodendoryx. Late stage in the closure of a pore, p.c, wall of pore canal; 
p.m., pore membrane, X 600. 
19 Lissodendoryx. Stage in the closure of a pore. X 600. 
20 Stylotella. Epithelioid lining of main efferent canal. Alcohol fixation. 
X 1200. 
21 Stylotella. Epithelioid lining of main efferent canal. Sublimate fixation. 
X 600. 
All figures have been reduced in reproduction by one-third. 
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