Phylum: Chlorophyta   Family: Volvocaceae

Pandorina morum  (O.F. Müller) J.B.G.M. Bory de Saint-Vincent, 1826

First described and illustrated by Müller (1786: 20, pl. 3: 14-16) as Volvox morum. It was later moved to its current position by Bory de Saint-Vincent (1826: 22).
Cell dimensions: Dia: 8-17 µm, Coenobia: 20-60 µm.
Common in slow-flowing waters, also in shallow lochs and ditches.

References: 
Bory de Saint-Vincent, J.B.G.M. (1826). Essai d'une classification des animaux microscopiques.
John, D.M., Whitton, B.A. & Brook, A.J. (2011 second edition). The Freshwater Algal Flora of the British Isles.
Müller, O.F. (1786). Animalcula infusoria fluviatilia et marina quæ detexit, systematice descripsit et ad vivum delineari curavit Otho Fridericus Müller ; sistet opus hoc posthumum, quod cum tabulis Aeneis L. in lucem tradit vidua ejus nobilissima cura Othonis Fabricii.