VOLYOX GLOBATOR. 
229 
oospore being smooth. The mode of fertilization of the latter 
form has not yet been directly observed. The genus is cosmo- 
politan, having been found throughout Europe, in North Africa, 
India, and North America. 
The old family of Volvocinese, which included the genera Vol- 
vox , Eudorina , Pandorina , Gonium , and Stejphanosphcera , is 
placed by Sachs, in the 4th edition of his 44 Lehrbuch,” under the 
Zygospores, and in the section characterized by the conjugation 
of zoogonidia (swarm-spores or zoospores). It is evident, however, 
that the family, as so constituted, cannot be maintained, and Ros- 
tafinski’s classification must be accepted as preferable, retain- 
ing those genera which exhibit the conjugation of swarm-spores 
as a family of Zygospores under the name of Pandorines, while 
the true Volvocines are placed in the class of Oospores,* in 
which the process of impregnation consists in the coalescence of 
one or more minute spontaneously motile antherozoids which 
escape from an antheridium, with a comparatively large oosphere 
contained in an oogonium. The process indeed bears a very 
close analogy to the mode of fertilization in one of the highest 
families of Oospores, the Fucaces. The family Volvocines, as 
thus constituted, includes at present only the two genera Volvox 
and Eudorina . The structure and developmental history of 
the latter have been described by Carter.f 
* This is the course followed in M'Nab’s recent class-hook of botanical 
classification. 
t “ Annals of Natural History,” 3rd series, Vol. ii. 1858, p. 237. 
EXPLANATION OF PLATE V. 
Fig. 1. A monoecious colony of Volvox globator'a, a 2 , a 3 , antheridia ; b, b 2 , 
gynogonidia ; b 3 , 6 4 , oospheres. 
Fig. 2. Ciliated peripheral cells. 
Fig. 3. a-e Parthenogonidia in successive stages of division. 
Fig. 4. Complete antheridium. 
Figs. 5 and 6. Antherozoids. 
Fig. 7. Oosphere containing antherozoids (see also fig. 1, b 4 ). 
Fig. 8. Fertilized oosphere. 
All the figures highly magnified. 
