44 
Some Aspects of the Alga. 
“ Polymorphism” and “Alternation of Generations” respectively. 
On Polymorphism Professor Oltmanns is very decisive, taking up 
Klebs’ position on the facts, and preferring, as we think rightly, to 
drop the much abused word altogether. “Fur mich,” he says, 
“ hat das wort aber einen so iiblen Beigeschmack, dass ich es am 
liebsten ganz streichen mochte, es hat zuviel Unheil gestiftet.” He 
shews, in fact, that so far as the phenomena are real at all they are 
better placed under other concepts. 
In his treatment of Alternation of Generations Professor 
Oltmanns adheres to the view of the “antithetic” origin of the 
Archegoniate sporophyte and regards the zoospores produced as an 
immediate result of the germination of the zygote in Hydrodictyon, 
Sphceroplea, ColeocJuete, CEdogonium, etc., as rudimentary develop¬ 
ments of the same kind, these zoospores (carpospores) being 
sharply separated from the zoospores produced by a potential 
gametophyte. With Klebs he denies the existence of a true alter¬ 
nation in VaucJieria, but in a case like Dictyota, he concedes the 
possibility of a “homologous” origin of the two generations. 
The chapter on “Adaptations” occupies a quarter of the whole 
book. It is pointed out that the external conformations of the 
Algae can be grouped in categories to each of which belong species 
of very various affinity. In some of these cases an attempt is 
made to find the adaptive significance of the vegetative form in 
question, while in others the author confesses his inability to do so. 
The forms distinguished are Shrub and Tree-forms, “ Mucilage-bush ”- 
forms, Whip-like forms. Net-algae, Leaf forms, Bladder forms. 
Dorsiventral Algae, Bolster-, Disc-and Crust-forms. Bryopsis is a 
good example of the common Bush or Tree form in which the whole 
plant-body may be compared with a leafless tree, or better, with a 
plant like Asparagus ; light has relatively free access to all assimi¬ 
lating parts of the plant. This is a useful arrangement in the case 
of plants like algie, the whole of whose bodies are, on account of 
the absorption of light by the medium, exposed to shade conditions. 
Various methods by which the different branches are kept apart 
are described. The “ mucilage-bush forms,” such as Cldorodetidron, 
Mischococcus, etc., are regarded as a special case in which the 
mucilage serves to keep the branches—here composed of separate 
cells—apart and relatively rigid. The Whip-forms ( Ulothrix , 
Himanthalia, etc.) are regarded as adaptations to water movement. 
Net-algae ( Hydrodictyon , etc.) on the contrary, are considered 
as adapted to the maximum bathing by the medium in still water, 
though in some cases ( Struvea , etc.) other factors are probably 
