800 QUARTERLY CHRONICLE OF MICROSCOPICAL SCIENCE. 
fresh-water alge, but even in the eyes of Schleiden it was 
quite void of significance—an “‘inessential” process. Yet it 
is obvious that it may be regarded as identical with fertilisa- 
tion if we suppose that the two elements which are necessary 
to take part in it are still undifferentiated ; the two conju- 
gating elements are indistinguishable, and have not assumed 
the forms and attributes of oospheres and antherozoids, of 
germ-cells and sperm-cells, 
If we take the processes of reproduction in Vaucheria or 
Saprolegnia as representative, those of the Conjugate and Zy- 
gomycetes may be compared with them as belonging to a 
simpler and probably primitive type. In each case a spore is 
produced as the result of the confluence, in the latter of 
similar, in the former of dissimilar elements. We may con- 
veniently term this spore a zygospore in the one case,an oospore 
in the other. ‘The researches of Thuret, Bornet, Tulasne, and 
Janczewski have further shown, that in all the higher Thal- 
lophytes the effects of fertilization are not limited to the 
production of a single spore, but set in action complicated 
processes of growth which give rise to structures of great 
diversity, including a great number of spores, and these 
may be called carpospores. 
From the point of view of the reproductive process we may 
therefore classify the mass of Thallophytes, as Sachs has 
done, with more or less certainty, into three large groups— 
ZYGOsSPORE®, OosPpoREH, CARpPospoREa. When this is 
accomplished it is found that in each group we have a series 
of Alge associated with a parallel series of Fungi. It only 
remains to throw into a fourth group, ProtopHyta, the 
organisms in which from their low degree of differentia- 
tion it seems probable that sexual reproduction has not made 
its appearance. 
The following pages contain, under the four classes estab- 
lished by Sachs, a brief account of the present state of our 
knowledge of the sexual reproduction of Thallophytes. 
Class I. PRoTroPpHYTA. 
In this class—which is to a certain extent no doubt pro- 
visional—those organisms are placed in which as far as is at 
present known spores are only formed by the segmentation of 
the protoplasm of a single parent cell (asexual reproduction) 
and not as the result of the fusion of segments of protoplasm 
derived from two distinct parent cells. 
CyanopHycE#®.—'This includes the same assemblage of 
organisms which Rabenhorst has classified as Phycochromo- 
phycee. The protoplasm of their cells is destitute of a 
