DESCRIPTION OF PLATE V. 
On the Structure and Development of Volvox globator, by Geo. Busk, Esq. 
1. Embryo Volvox, in which the contents are divided into four segments. 
2. Ditto, in vp-hich segmentation has proceeded to the formation of 
numerous segments, each furnished with several amylaceous 
spherules. 
3. Ditto, after segmentation is completed, but before the appearance of 
cilia. 
3. * Portion of the edge of an embryo Volvox viewed in the equatorial 
plane, showing the cilia perforating the outer tunic, but not passing 
beyond the external gelatinous (?) envelope. 
4. The same when tested by solution of iodine. 
3. Portion of the edge of mature Volvox (var. vulgaris) viewed in the 
equatorial plane and representing three zoospores in situ. The 
faint lines between indicate the limits of the gelatinous envelope 
of each zoospore, the junctions of which are indicated by the 
hexagonal areas of Mr, Williamson. (These intermediate lines have 
been added to the figure since the original production of the paper.) 
6. Mature zoospores, undergoing " deliquescence." 
7. Zoospores in which the contractile vacuole is still present. 
8. "Winter spores" of V. aureus, a, in the earlier state; &, when 
matured. 
9. Contents of mature winter spore, affected by solution of iodine. 
a, amylaceous granules ; Z>, yellow oil. 
10. More highly magnified view of a winter spore compressed, to show 
the double tunic. 
11. The same crushed, and treated with iodine and sulphuric acid. 
12. A portion of the edge, to show the granular fluid (as rendered so by 
iodine) between the outer and inner tunics, a, granular fluid ; 
&, interior of spore. 
13. Portion of wall of Sphoerosira Volvox. 
14. Zoospores in different stages of development, a, one fully divided, 
seen on the side ; h, the same viewed from above ; c, one in which 
segmentation has proceeded only to the second division. 
15. " 
16. 
17. 
18. 
19.. 
20. More highly magnified view of the same — where there is apparently 
a second coat in process of being thrown off from the central mass 
of protoplasm. 
21 I 
or)' I A series of changes undergone by the same zoospores in the course of 
j twenty-four hours. 
Fig. 22 shows the partial dropsy of the cell, but which did not 
proceed further. 
24. Professor Williamson's hexagonal areolation. 
25. Ditto under iodine. 
26. Appearance assumed by the zoospores in the early state, where, owing 
to abundant nutrition, the quantity of protoplasm is very abundant. 
This form gradually passes into the ordinary, and it is in this state 
that the contractile spaces are most advantageously to be sought. 
27. Shows the situation of the contractile vacuole in a connecting band. 
Series of changes occurring in the hydropical condition of zoospores. 
