SEXUAL REPRODUCTION OF THALLOPHYTES. 301 
nucleus, and besides containing chlorophyll is tinged with 
the peculiar blue colouring matter, phycocyan. The subor- 
dinate families are Chroococcacee,! Oscillatoriacee, Scyto- 
nemee, Nostocacee and Rivulariacee. 
PALMELLACE# differ principally from Cyanophycez in the 
absence of an obvious blue colouring matter masking the 
chlorophyll. Some genera, as Gleocystis and Tetraspora 
develope zoospores. Like Protococcus and Pleurococcus 
these will probably have to be removed to the Zygosporee. 
EvGLENEx must be placed in this group; they are not 
known to possess a sexual reproduction, otherwise they might 
be associated with Pandorinez in the next class. 
Fungi contribute to the Protophyta the group of Schizo- 
mycetes? (Bacteria), which have some affinity with Oscilal- 
toriacee® and in some respects with Saccharomyces (yeast). 
Class II. Zycosrorem. 
We here meet with the simplest mode of sexual repro- 
duction—conjugation. In some cases an incipient differen- 
tiation of the two conjugating elements may be noticed as in 
Pandorina and Zygnemee. Indeed, in all the series there 
is probably a disposition to progress towards the degree of 
differentiation which belongs to the Oosporec. 
Two divisions may be conveniently made according as the 
conjugating cells are motile or non-motile. 
A. Conjugating cells motile. 
Amongst the green alge the number of forms in which the 
zygospore has been ascertained to be produced by the conju- 
gation of two zoospores is gradually receiving additions. In 
all these cases it may be stated more or less generally that 
the zoospores which are produced by the successive segmen- 
tation of the protoplasm of a vegetative cell are of two kinds 
which have been named respectively macrozoospores and 
microzoospores. While in some cases it would appear as if 
the difference between these merely depended on the degree 
to which the successive segmentation of the contents of 
similar cells is carried, in others the different kinds of zoo- 
spores are produced from different kinds of filaments or 
perhaps even from different individuals. 
The function of the macrozoospores is purely vegetative. 
' Bornet has figured the spores of Glzocapsa, * Ann, des Sc. Nat.,’ 5e 
sér., tom. xvii, Pl. 16, fig. 3. 
* On “ Bacteria,” see ‘ Quart. Journ. Mic. Sci., 1873, p. 156. 
3 On “Saccharomyces,” see ‘Quart. Journ, of Mic. Sci.,’ 1875, p, 142. 
