NATURAL SCIENCE, VOL. XIII. PLATE III. 
THE STRUCTURE OF DIATOMS, AFTER LAUTERBORN. 
Fig. 1.—Transverse section through Pinnularia major in the region between the extremity of the cell 
and the median mass of protoplasm (combination figure). Ch., chromatophore ; zc., chambers (‘ Riefen’) 
on inner surface of cell-wall; 7., raphe; vac., vacuole. 
Fig. 2.—Transverse section through one valve of the frustule of P. major. The section passes between two 
of the chambers, so that the contour of the cell-wall is unbroken except at 7’, the raphe. 
Fic. 5.—Traus\erse section through the raphe, from another section, showing an apparent closure of 
the cleft internally. 
Fie. 4.—Median transverse section through Surrirella caicarata (combination figure). At a, the 
section passes through one of the intermediate pieces in the ala, ata,, it just encroaches upon one of the 
transverse canals; @,, a,, two transverse canals bisected ; ch/., superficial lobular process of chromato- 
phore; Zc., longitudinal canal; nw., nucleus. 
Fic. 5.—Surface view of a portion of one of the alae of S. calcarata. Ch., process of chromatophore sur- 
rounded by protoplasm ; /c., longitudinal canal; mp., intermediate piece; pa., unicellular alga; trc., trans- 
verse canal. 
Fie. 6.—Lateral view of Pinnularia major moving in an emulsion of Indian Ink. 
Fig. 7.—Surface view of the same. Cn., central node; gs., anterior granule streams; gt., gelatinous 
threads with adhering granules; 7., raphe; ¢v., terminal node. 
Fic. 8.— Resting example of Pinnularia in concentrated emulsion of Indian ink (lateral view); ge., 
gelatinous envelope. 
