Notes. 
373 
Comparing Oedogonium with Coleochaete (also true of Bulbochaete ), 
we find that as in some species of the latter we have a filamentous 
Alga reproducing itself both sexually and asexually, and, as in 
Coleochaete , the individuals produced by the asexual method are 
precisely similar to the parent plant; if we turn to the sexual re- 
production we find that the fertilized ovum or oospore does not directly 
produce an individual similar to the parent, but it divides into several 
cells each of which becomes a spore and germinates ; so that several 
Oedogonia are formed. The oospore therefore here behaves just as 
in Coleochaete , consequently it is evident that in Oedogonium we have 
an alternation of generations. The mass of cells produced by the 
division of the oospore is a sporophore just as much as in Coleochaete . 
In Sphaeroplea annulina we have a very significant case; the 
oospore divides into several cells each of which gives rise to a new 
Sphaeroplea filament. The asexual reproductive cells formed by the 
division of the oospore are the only asexual method of reproduction 
possessed by this Alga. So that in Sphaeroplea the alternation of 
generations is as complete as in the Mosses or higher plants, for the 
sexual generation reproduces sexually only, and the mass of cells 
formed by the division of the oospore, which must be regarded as a 
sporophore, forms only spores. 
In the Volvocineae, Hydrodidyon also exhibits alternation of 
generations, for its oospore gives rise to two or four spores, each of 
which gives rise to separate Hydrodidyon plants. 
Pandorina is perhaps the most instructive form of all ; for the 
oospore may either develop directly into a single Pandorina coenobium, 
or it may divide into two or more cells each of which becomes a 
spore and develops into a separate Pandorina. In the former case 
there is no alternation of generations; in the latter, where several 
coenobia are developed from one oospore, there is an alternation of 
generations. The life-history of Pandorina is, in the latter case, 
essentially similar to that of Coleochaete. The sexual or oospore 
generation can reproduce itself both sexually and asexually, and the 
sexual process ultimately results in a body consisting of several cells, 
spores, each of which gives rise to a new sexual individual, and, as in 
Coleochaete , cannot reproduce sexually. It also must therefore be 
regarded as a sporophore. 
The consideration of the life-histories of the Algae of which I have 
just given a brief review shows, I think, in what alternation of 
