in Cephalopoda (Siphonopoda) . 



305 



tinuous ; it shows a corresponding increase in thickness ; its 

 distinction from the upper part of the cell is not, however, 



Fig. 1. — Siuuous partitions (ff.p.) appearing near margin of shell through 

 membranes (■/«.). M.P. is the edge of the middle plate folded 

 over. (Seen with 1-inch objective, reflected light.) 



Fig. 2. — Shows relation of fi-ee-stretched membranes (/".?».) to a sinuous 

 partition (s.p.), which is cut at right angles. Its ventral end is 

 enlarged and abuts on a lamella or septum (/.) composed of 

 membranes (w.) and arragonite. (Stained borax-carmine, and 

 examined by polarized light, seen with Zei>s D objective.) 



Fig. 3. — Cells lining mantle, from 3 in fig. 6. (Stained haematoxylin.) 



Fig. 4. — Cells from 4 in tig. (5. 



Fig. 5. — Cells from 5 in fig. 6. 



[Figs. 4 and 5, drawn as stained with borax-carmine, were also studied 

 with hfematoxylin and methyl-green. Figs. 3, 4, 5, as seen by 

 transmitted light under g-inch objective of Swift.] 



Fig. 6, — Sagittal section of anterior portion of shell enclosed in shell-sac ; 

 shows relations of figs. 2, 3, 4, and o. The calcified portion is 

 shaded with diagonal lines, as in fig. 2. (Seen with 1-inch ob- 

 jective.) 



N.B. — The orientation of figs. 3, 4, 5, 6 is the same; fig. 2 is reversed. 

 All the figures are drawn to nature except the shell-part of 

 fig. 6, which is supplied from very many sections and drawings. 



Where the edge of the shell is reached these 

 The conclusion that these 



quite so clear 



remarkable cells suddenly stop. 



