866 WILLIAM ARCHER. 



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 family, the cells still connected in 

 the middle by the angles, the de2:)th 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 margins of the side 

 lobes of the cell somewhat emarginate at the middle. 



Fig. 5. A four-celled family, the tablet (Scheibchen) fur- 

 nished 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 continu- 

 ous division [no further reference 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, represents a distinct species, of which, however, I 

 [Professor Reinsch] have observed bnt a single specimen ; 

 the cell cruciate, formed of four semicircular lobes ; bnt 

 Avhether the cells represent the developed condition, or the 

 condition of beginning of a new division, I [Professor Reinsch] 

 do not venture to decide ; the dimensions as in a four-celled 

 family of the ordinary form. 



Tetrapedia Crux-Michaeli (Reinsch). 

 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 sctigera (Arch.). 



Figs. 14, 16. Front or broad view. 

 Fig 17. Side view. 



Fig. 18. A minute Nostoc, with spores. 



