230 American Quarterly Microscopical Journal. 



Their spherical forms and chlorophyll-green color make them 

 closely resemble the unicellular Algae. They possess, like the 

 swarm-spores of the latter, two or more moving filaments in 

 front, but besides these they have one or more contractile, slow- 

 ly pulsating vacuoles, and generally a red pigment spot. Single, 

 or in families, surrounded with a gelatinous investment, they are 

 in voluntary motion during the greater part of their life, 

 only coming to rest for the purpose of propagation. The 

 alga spore, on the contrary, after a short period of activity, 

 soon comes to rest and grows into the original form, and can 

 never again return to the moving condition. However, we 

 find also motion in some Phycochromaceae and Diatomaceae 

 during the greater part of their lives, but very rarely. 



If the Volvocineae are to be regarded as Algae, however, the 

 Flagellata may also be placed with them according to A. 

 Braun and v. Siebold, while still others would place the 

 Volvocineae among the Algae but not the Euglenae and Peridinae. 



ORDER IV. CONJUGATE. 

 Cells single, or in filamentous families, without terminal growth, and 



not branching; multiplication and propagation by simple cell division, 



and resting-spores which form as the result of copulation of two cells, 



by the union of their entire contents (Zygospores). 



No ^arm-spores. [Endochrome usually arranged in patterns.] 



Cells cylindrical, not constricted in the middle, in 



families, copulating filaments. Zygnemace^, Endl 



Cells of varying form, usually divided by a con- 

 striction in the middle, copulation only be- 

 tween isolated cells. Desmidiace/E, Ktz 



I. FAMILY. ZYGNEMACE^. 



Cells cylindrical, in filaments, swimming free, forming loose, green 

 masses. Nucleus often very prominent in the center of the cell, 

 surrounded by star-like radiating strings of plasma reaching the 

 walls; chlorophyll in plasma lining the cell-walls, often arranged in 

 ornamental bands, or groups, with distinct, large, starch-grains. 



Copulation between two neighboring cells of the 



same filament ; chlorophyll in spiral bands. Rhynchonema, Ktz. 



Copulation between two cells of different fila- 

 ments, 



ladder-like, from numerous cell-unions. 

 Spore in one of the copulating cells, 



chlorophyll in spiral bands. Spirogyra, Link. 



