DESCRIPTION OF PLATE III. 

 In illustration of Dr. Allman's Paper. 



Figs. 1 — 8. Aphanizomenon Flos-aquoe. 



fig. 



1. — Fascicles of filaments, natural size. 



2. — Three primary fascicles united into a larger bundle, magnified. 



3. — The fascicles have broken up into their component filaments, which 



have rearranged themselves into parallel wavy curves, slightly 



magnified. 

 4. — A filament with two sporangia. 



a, a, ordinary cells. 



b, h, sporangia. 



5. — A filament with a heterocyst. 



a, a, ordinary ceils. ip^ 



b, b, heterocyst. " 

 6. — Filament with a heterocyst after the application of a solution of 



iodine. 



a, ordinary cells, 



b, heterocyst. 



7. — A sporangium after the application of a solution of iodine. 

 8. — Portion of a filament in which several ordinary cells seem to be in 

 process of coalescence, in order to form a sporangium. 



Figs. 9 — 17. Periclmea uherrima. 



9. — P. uberrima in the act of swimming, viewed from the side of the 

 vertical furrow. The ocelliform spot and nucleus are visible 

 through the walls. 

 10. — The same viewed from the opposite side. 

 11. — The animalcule after having passed from a motile to a quiescent 



state. 

 12. — The animalcule with the external vesicle ruptured, and the contents 

 escaping. 



a, a, oil-globules. 



b, nucleus, 

 c, c, brown granules. 

 13. — The nucleus isolated. 



14. — The animalcule undergoing transverse division. 

 15. — The same after the application of a solution of iodine. 

 16. — Outline of micleus, with commencement of transverse division. 

 17. — Transverse division nearly completed. 



