[ref. ID; 1618]
Stalked individuals form colony; frequently attached to animals such as copepods, rotifers, etc.; stalk mucilaginous; individual cells pyriform, ellipsoidal or cylindrical; without flagellum; a single flagellum only in free-swimming stage; discoidal chromatophores numerous; with pyrenoids; multiplication by longitudinal fission; also by swarmer, possessing a flagellum and a stigma; fresh water. (ref. ID; 1618)

• Colacium arbuscula Stein
  See; Colacium vesiculosum var. arbuscula (ref. ID; 4950)
• Colacium arcuatum Playf. (ref. ID; 4950)
• Colacium calvum Stein (ref. ID; 4950)
• Colacium cyclopicola (Gicklhorn) Bourrelly (ref. ID; 3517, 4950)
  Syn; Euglena cyclopicola Gicklhorn (ref. ID; 4950)
• Colacium elongatum Playfair (ref. ID; 4950)
• Colacium epiphyticum Fritsch (ref. ID; 4950)
• Colacium gojdiscae (Prescott) Huber-Pestalozzi (ref. ID; 4950)
  Syn; Euglena goidiscae Prescott (ref. ID; 4950)
• Colacium mucronatum Bourr. & Chad. (ref. ID; 4950)
• Colacium ovale Playf. (ref. ID; 4950)
• Colacium parasiticum (Sokoloff) Huber-Pestalozzi (ref. ID; 4950)
  Syn; Euglena parasitica Sokoloff (ref. ID; 4950)
• Colacium physeter (Fott) Fott
  See; Euglena physeter (ref. ID; 2671)
• Colacium pyrenophorum Bourr. (ref. ID; 4950)
• Colacium sanguineum Lackey (ref. ID; 4950)
• Colacium sideropus Skuja (ref. ID; 3517, 4950)
• Colacium simplex Huber-Pestalozzi (ref. ID; 4950 original paper)
• Colacium vesiculosum Ehrenberg (ref. ID; 1618, 3517, 4950)
• Colacium vesiculosum f. arbuscula (Stein) Huber-Pestalozzi (ref. ID; 1618, 3517, 4950)
  Syn; Colacium arbuscula Stein (ref. ID; 4950)
• Colacium vesiculosum f. natans (Lemm.) H.-P. (ref. ID; 4950)