Archer— Ow the Genus Tetrapedia. 
809 
that can accompany them will be simply a direct translation, though 
not taken in precisely the same order, from the original : — 
Tetrapedia Gothica (Reinsch). 
rig. 1. A simple developed cell (Plate XXL), whose lateral 
margins present the indication of division. 
Fig. 2. A cell with the indication of division, the angles bluntly 
rounded. 
Fig. 3. A cell [the division] somewhat more advanced. 
Fig. 4. A four- celled famil}^, the cells still connected in the middle 
by the angles, the depth of the incisions almost the breadth of the cells, 
the individual cells almost fully-formed — that is to say — already with 
the commencement of a division into a new cell-generation, the mar- 
gins of the side- lobes of the cell somewhat emarginate at the middle. 
Fig. 5. A four-celled family, the tablet (Scheibchen) furnished at 
the middle with a quadrangular hole (Loch). 
Fig. 6. A sixteen -celled family, formed from four smaller families, 
still connected at the corresponding angles, all the cells of like figure, 
and presenting the indication of continuous division [J^o further refer- 
ence is made on the part of the author to the holes]. 
Fig. 7. Side view of a cell. 
Fig. 8. A four-celled family of peculiar form, which perhaps re- 
presents a distinct species, of which, however, I [Professor Reinsch] 
have observed but a single specimen ; the cell cruciate, formed of four 
semicircular lobes ; but whether the cells represent the developed con- 
dition, or the condition of beginning of a new division, I [Professor 
Eeinsch] do not venture to decide ; the dimensions as in a four-celled 
family of the ordinary form. 
Tetrapedia Crux-Michaeli (EeinschJ. 
Fig. 9. An individual in the state as observed, showing the division 
furthest advanced. 
Fig. 10. Side view of the same individual. 
Tetrapedia Reinschiana (Arch.). 
Figs. 11, 12. Front, or broad view. 
Fig. 13. Side view. 
Tetrapedia setigera (Arch.). 
Figs. 14, 16. Front, or broad view. 
Fig. 17. Side view. 
Fig. 18. Portion of a filament of a minute Nostoc, with spores. 
