NATURAL SCIENCE, VOL. XIII. 



Plate III. 



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Tin Stkui hi:k 01 Diatoms, after Lai i iximi.-s. 

 i sverse section through Pinnularia major in the region between the extremity of the cell 



ami the median mass of protoplasm (combination figure). Ch., chromatophore ; ic, chambers ('Riefen') 

 (ii inner surface of cell-wall ; r., raphe; rac., vacuole. 



Fig. 2.- Transverse section through cue valve of the frustule of /'. major. The section i asses between two 

 of the chambers, so that the contonr of the ce I- wall is unbroken except at /■. the raphe. 



■. — Trans n through tin- raphe, from another section, showing an apparent closure of 



the cleft internally. 



Fig. 4. — Median transverse section through Sun i (combination figure). At a, the 



le of the intermediate pieces in the ala, ata 2 . it just encroaches upon one of the 

 transverse canals; " .. a 4 , two transverse canals bisected; eA/., superficial lobular process of chromato- 

 phore; lc, longitudinal canal; nu., nucleus. 



Fig. 5.- Surface view of a portion ol one of the alae of S. calcarata. Ch., process of chromatophon 

 rounded by protoplasm ; lc, longitudinal canal ; mp., intermediate piece; pa., unicellular alga ; trc, trans. 

 anal. 

 Kio. i;.— Lateral view of Pinnularia major moving in an emulsion "f Indian Ink. 

 Fig. 7. — Surface view of the same. ''«., central node: gs., anterior granule streams: ;/(.. gelatinous 

 threads with adhering granules; r., raphe; In., terminal node. 



Fig. 8.— Resting example of Pinnularia in concentrated emulsion of Indian ink (lateral view); <je., 

 gelatinous envelopi . 



