DESCRIPTION OF PLATE VI. 
On the Structure of Vol vox globator, hy Professor W. O. Williamson. 
The same letters of reference are employed throughout to indicate the 
same structures. 
21 Cells of the stellate var. of Volvox in different stages of the con- 
g*> traction of the protoplasmic threads, "a, outer cell- wall ; pro- 
^'j toplasm ; e, connecting threads ; g, cilia. 
5. Section of Volvox^ with its ciliated parietal cells. /, vesicles in 
which the ciliated gemm£e are developed. Two of the gemmse 
seen out of focus. 
6. Young gemma ruptured by pressure, h, detached protoplasms ; 
/, vesicles within which the gemma is developed ; c, protoplasmic 
membranes of three segments of the gemma. 6, granular and 
mucilaginous matter escaping from the ruptured segments. 
7. Portion of a Volvox mounted in glycerine and viewed obliquely. 
a, cell- walls ; 6, protoplasms ; c c, protoplasmic membranes ; e, col- 
lapsed connecting threads. 
8. Similar cells, in which the protoplasmic membrane is more distended. 
Eeferences as before. 
9. Specimen in which the threads appear to traverse the intercellular 
spaces. Eeferences as before. 
10. Ordinary appearance of the var., with spherical protoplasms. 
11. Specimen of the same mounted in glycerine. 
12. Probable section of living Volvox. d, superficial pellicle. 
13. Probable section of fig. 11. 
14 1 
^g'l Sections of figs. 1-4, after being mounted in glycerine. 
16. Detached cells from the same, viewed superficially. 
17. Similar specimen, in which the cells are invisible — the protoplasmic 
membranes alone being seen. 
