62 COCCOPHYCE. 
ruptured sphere, and seems to show that there is a denser layer of 
thick matter, whatever its nature may be, disposed in a somewhat 
regular manner, being concentrated near the south pole of the axis of 
rotation, whence it spreads over the inner surface in streaks resembling 
the lines of longitude on a terrestrial globe. 
“ Both from its position and from the rapidity with which it is stained 
by aniline purple, without which its existence is apparently absolutely 
undemonstrable—(in which respect it is in marked contrast to the outer 
cell-wall, which latter is only faintly tinted by somewhat prolonged 
application of the reagent, and then only where the hexagonal structure 
exists)—I have no doubt that this inner layer is the true ‘ primordia 
utricle’ of the cell, and possesses that character of vital and formative 
matter which distinguishes this element of cell-structure from the outer 
wall, which, on the other hand, probably consists of cellulose or some 
similar corapound. Probably the arrangement of this inner layer, in 
radiating lines or ribs, contributes to the elasticity of the fabric, whereby 
it is enabled to open at a given point for the escape of the young, and 
to contract again after their emission. 
“The increase of individuals by the means already described is 
strictly an instance of subdivision. 
“ But Volvoz globator also affords an instance of true alternation of 
generations. As may probably be affirmed of all living organisms, its 
life-history would be incomplete without a process of sexual reproduc. 
tion, and accordingly, after a long sequence of asexual generations, a 
strictly sexaal process intervenes, from which result certain spores 
destined to lie dormant for w while, and, like the zygospores of the 
Conjugate Alge, to resist vicissitudes of condition and climate 
through the rigours of winter, and then to produce the parent form in 
the succeeding year, when external conditions again favour its develop- 
ment. 
“ Cohn fully traced the various stages of this process, and described 
them in the ‘ Beitrage zur Biologie der Pflanzen’ (1875, Vol. I., Heft. 3), 
and in the ‘Annales des Sciences Naturelles’ (4 iéme Ser. Bot., Tom. 
V., 323); and his observations have been more or less confirmed by 
other investigators, especially by Carter (Ann. Nat. Hist., 8rd Ser., Vol. 
IIT., 1859, p. 1), and more recently, in 1877, by a French botanist, M. 
F. Henneguay. 
“Cohn and Carter both hold that there are two varieties of Volvox,* 
one moncecious, the other dicecious, and the latter maintains that 
Spherosira Volvow is the male form of the dicecious sub-species. Be 
that as it may, the reprodactive process in the moneecious form is as 
follows:—The sexual reproductive cells, male and female, occur in 
spheres of unusual size in the autumn, and are few in proportion to the 
number of sterile cells, and the reproductive process does not occur 
simultaneously with, but as a climax to a long series of asexual genera- 
tions. On their first appearance the gynogonidia or female cells are 
about three times the size of the sterile ones, of « deep green colour, 
and of a frothy consistency from abundance of vacuoles. They are 
easily distinguished from the parthenogonidia by their never sub- 
dividing. (Plate 22, Fig. 5b.) They next become flask-shaped, their 
narrow end touching the periphery of the sphere, and the broader end 
hanging free in the internal cavity. (Plate 22, Fig. 52.) Finally, they 
assume a spherical form, and become oospheres, each enveloped in a 
gelatinous membrane. (Plate 22, Fig. 503, b+.) 
“The androgonidia, or male cells, at first closely resemble the par- 
thenogonidia, but undergoing division in two instead of three directions, 
* The two forms are here accepted, after Stein, as Folvor globator and Volvoz 
minor. 
