The Classification of the Algae. 9 ! 
emphasise the phylogenetic importance of the motile cell and 
its consequences in accordance with Bohlin’s principles to which 
we have just called attention afresh. In the view of the authors of 
the “ Revision,” the Conjugatae are an isolated group of pure green 
forms whose origin is very doubtful and which are fundamentally 
distinguished from the other “ pure green ” phyla by the fact that 
their reproductive cells have no ciliation. The possibility of their 
union with the Diatoms appears to the authors of the “ Revision ” 
to be excluded by the difference of pigment (apart from other 
characters) since all the evidence appears to point to pigment as of 
absolutely the first importance as a taxonomic character. Since 
Professor Oltmanns does not adhere to this view it would have been 
better if he had avoided the term Akontae altogether and called his 
composite Conjugatae-Bacillariales group simply Zygophyceae (a 
name he has given as an alternative). The use of Akontae in this 
sense introduces a further confusion in nomenclature which it was 
the object of the authors of the “ Revision ” to simplify on the 
promising lines established by the Swedish Algologists. 
In his classification of the difficult group of the Conjugatae, 
Professor Oltmanns deviates somewhat from previous arrangements. 
He includes Genicularia and Gonatozygon, usually placed with the 
Desmids, in the filamentous group (Zygnemaceae). This is a change 
in the same direction as that made in the “ Revision ” where these 
genera are placed in a separate family Archidesmidiaceae, intended 
to connect the filamentous forms with the more specialised Desmids. 
Professor Ottmanns goes further, and himself makes a separate 
group—the Mesotaeniaceae—in which he places the genera 
Mesotaenium, Spirotaenia and Cylindrocystis, characterised by simple 
membranes and the production of four embryos from each zygote. 
These three genera, though nearer the Desmids proper than 
Genicularia and Gonatozygon , are certainly the least specialised forms 
of the latter. They exhibit the three types of chromatophore found 
in the filamentous forms, while most of the other Desmids shew 
some combination of plates and ridges. Professor Oltmanns 
considers that his Mesotaeniaceae are the simplest and most 
primitive Conjugates (p. 53) and (if Genicularia and Gonatozygon 
are placed with the filamentous forms) they certainly seem to 
connect the Desmids and Zygnemales. He lays more stress on the 
mode of conjugation than on the form of the chromatophore, deriving 
the method of gamete union found in Closterium from that described 
by Archer in Spirotccnia and the Zygnemaceous type from that 
found in Cylindrocystis. He points out that a common character of 
