REPRODUCTION IN LOWER PLANT LIFE. 105 
to take place even within the gametange, more than two 
sometimes uniting together. The larger zoospores are 
quadriflagellate. In Pandorina (Pandorinee) (fig. 6), the 
only known mode of sexual reproduction is by the con- 
jugation of zoogametes within the parent-colony; among 
the throng of swarm-cells pairs may be seen approaching 
as 1f they were seeking one another; these ultimately 
come into contact by their pointed extremities, and 
coalesce. In Hudorina (Volvocinez) (fig. 7), which re- 
sembles Pandorina very much in appearance, a much 
greater advance is shown in the differentiation of the 
sexual elements. The colony or coenobe is, in both these 
fresh-water Algz, a nearly spherical body, rapidly propelled 
through the water by the numerous long, delicate flagels 
which project through its envelope. In Pandorina these 
belong to the zoogametes, in Mudorina to the female 
elements only, affording, therefore, one of the rare 
instances in the vegetable kingdom of zoospheres, 2.e., of 
female cells endowed with motility by means of flagels. 
The male elements or antherozoids are elongated fusiform 
bodies of protoplasm, closely resembling those of Volvoz, 
and formed in special daughter-colonies entirely enclosed 
within the coenobe, which may, therefore, be called 
antherids. The antherozoids swarm round the zoo- 
pheres until their flagels become entangled in those of the 
latter ; they then force their way through the gelatinous 
envelope of the oogone, and, finally, coalesce with the 
zoospheres. A most instructive observation has, how- 
ever, recently been made by Dangeard, that the oospheres 
occasionally act as zoogametes, coalescing with one 
another. In the familar Volvox (Volvocinez) (fig. 8) 
we have a further most interesting advance. The female 
elements have lost their flagels, and become ordinary 
motionless oospheres, which are impregnated by the 
