Volvox and Associated Algae from Kimberley. 521 



PLATE XXXVI. 



Sphaerocystis Poweri sp. nov. 

 FIG. 



A. Early stage, " Eudorina Form," with a Juvenile colony of V. Roussdetii f. 



griquaensis containing a nearly mature embryo (702). 



B. Large colony of the typical spherical form containing 32 groups of 32 cells 



each (611). 



C. D. 16-celled groups from a mature spherical colony in which some of the 



cells are dividing to form sub-groups, also 16-celled, preparatory to the 

 formation of daughter spheres. Stained with methylene blue to show the 

 enveloping membranes. The large pyrenoid shows clearly (663, 661). 

 E. Group showing various forms and stages. On the left a young typical sphere ; 

 in the centre a large sphere in which the cells of the groups have divided 

 and the daughter colonies rounded off, the outer membrane of the parent 

 is firm, the inner gelatinous matrix partially collapsed, membranes of the 

 daughters thin but firm. Some of the daughters have already escaped, 

 two of these appearing on the right. Round the edge are portions of rounded 

 and lobed masses of the palmelloid stage or " Tetraspora Form " (681). 

 A x 100. B x 54. C, D x 325. E x 45. 



PLATE XXXVII. 

 Sphaerocystis Poiveri. 



A. Sphere containing daughter colonies entering transition stage to palmelloid 



condition ; zoospores and young cells in peripheral layers (693). 



B. Two colonies of the " Botryoidal Form " (683). 



C. Cells and zoospores from a colony of the Tetraspora type. Larger cells mature, 



smaller still in groups derived from the division of older cells : on the right 

 one zoospore shows clearly (696). 



D. E. Transition from spherical to palmelloid form. In D the four young 



colonies in the centre have escaped from the colony above ; on the left is a 

 colony in which cells from the groups have divided to form zoospores which 

 have migrated to other parts of the matrix and have there settled down 

 and rounded off. On the right, portions of two other colonies in the transition 

 stage (697). 



In E, in the centre, is a typical sphere of 32 groups, some of which contain 16 

 and some 32 cells ; round it are two transition stages and two colonies of 

 the Tetraspora type showing crowding of the cells within the gelatinous 

 envelope. Stained with iodine (704). 



A xlOO. B x70. C x400. D, E x38. 



VOL. XVI, PART 3. 34 



