33. In colonies 34. 

 Single individuals 41, 



34. Colonies plant'like, branching; each animal of colony enclosed in a trans- 



parent sheath or lorica 



Dinohryon Ehrenberg 

 Colonies plate-like or spherical 35. 



35. Colony plate-like; flagella on one side only 



Gonium Miiller 

 Colony almost or quite spherical; flagella not limited to one side 36. 



36. Cells of the colony reaching to the center 37. 

 Cells of the colony distributed around the surface of a sphere 38. 



37. With many cells loosely joined, with no common envelope 



Synura Ehrenberg 

 (Uvella) 

 With sixteen to thirty-two cells enclosed within a common envelope 

 Payidorina Bory 



38. Individuals very numerous, pear-shaped, each usually with two yellow 



chromatophores 



Uroglenu Ehrenberg 

 Individuals spherical, each with many green chromatophores 39. 



39. With all cells of the colony of uniform size 



Eudorma Ehrenberg 

 With many small vegetative and large reproductive cells present 40. 



40. With the small, vegetative cells at one end of the colony and the large, 



reproductive cells at the other 

 Pleodorina Shaw 

 With the large and small cells mixed 

 Volvox Linn. 



41. With a membrane of distinct plates covering the animal 42. 

 No plates 43. 



42. Body ovate 



Peridimum Ehrenberg 

 With long, horn-like processes on the plates 

 Ceratium Schrank 



43. Body with one large green chromatophore 



Chlaynydomonas Ehrenberg 

 Body almost uniformly colored brown or green 44. 



44. Body encased in a thick sheath and only slightly flexible: color brown 



Trachelomonas Ehrenberg 

 Body flexible, not encased in a thick sheath; color green 45. 



45. Body globular to cylindrical, widest in the middle, not flattened 



Euglena Ehrenberg 

 Body flattened, widest at the front end 

 Phacus Nitzsch 



41 



