Blackman and Tans ley. 
216 
5. Gonatonema. Wittrock, 1878. 
Vegetative cells as in Mougeotia, but reproduction by 
increase of vegetative cells to double their original 
length, division of the cliromatophore in the middle, 
swelling of the cell wall at that point, and finally 
collection of most of the cell contents in the swelling, 
which is then cut off as an “ aplanospore.” 
[The cytological details of the process of “ aplanospore ’’-for¬ 
mation in this genus have not been followed, but tbe sequence of 
events strongly suggests that the so-called aplanospore is really a 
zygote, produced by isogamous conjugation of gametes whose mother- 
cells have never been separated by a wall.] 
Class IV.—HETEROKONTAE. 
Organisms unicellular, multicellular, or coenocytic. Cell of 
“flagellate ” or of algal organisation , containing rarely one, usually 
many discoid, parietal, yellow-green chromatophores , devoid of pyrc- 
noids and starch. The usual anabolite is an oil. The motile 
individual cells or the zoospores are provided with two flagella either 
unequal in length or opposed in direction, arising from a spot a little 
to the side of the anterior end. The motile cells generally exhibit 
amoeboid or “ metabolic ” movement. 
Series I. Chloromonadales. 
Organisms, either unicellular and motile or united to form a 
mucilaginous colony. Cells of “flagellate ” organisation, devoid of 
typical cell-walls and dividing longitudinally. Resting cells occur : 
gamogenesis does not take place. 
[Though the members of this series must be considered to be Fla- 
gellata and not Algse (see p. 22 ), it is not possible to omit them from 
this scheme of classification, since they represent the primitive organisms 
possessing Heterokontan characters from which the next two series have 
been evolved.] 
Fam. I. Chloramoebaceae. 
Flagellate cells , free-swimming, naked, with a belt of discoid 
chromatophores. Flagella very unequal in length, the short one curved 
sideways. Vegetative division takes place probably in the motile state. 
Resting cells with thick walls occur. 
Genus. 
Chlor amoeba. Bohlin, 1897. 
Cells round to ellipsoid, very amoeboid, with one con¬ 
tractile vacuole and two to six chromatophores, usually 
nourished liolophytically, but also capable of living 
saprophytically in the dark in solutions of sugars, etc., 
and then devoid of assimilatory pigment. 
Fam. II. Vacuolariaceae. 
Flagellate cells naked free swimming and predominantly motile, 
but division takes place only in the non-motile condition, within a 
mucilaginous investment Chromatophores numerous. Flagella two, 
