108 NATURAL SCIENCE [August 
tions. The description of new species and genera of lower algae went 
quietly forward till Cienkowski published in 1876 his observations 
on the palmella-condition of the filamentous algae, Stigeocloniwm, 
Ulothrix, etc. These very reliable observations seemed to prove 
that lower algae are only developmental stages of the filamentous 
forms. Cienkowski himself, and other workers also, went so far 
as to express doubt. as to the independence of most unicellular 
green algae. In order to decide the question, I established from 
1879 to 1881 many cultures of these forms. My observations, 
from which I published a short extract in 1883, showed that the 
lower algae, treated by the methods then accessible to me, were as 
much independent organisms and remained as constant as any 
higher plant. The common, universally distributed organism, 
Pleurococcus vulgaris, for instance, reproduced itself only by 
vegetative division, and it could not by any method be converted 
into another alga. Artari (1892) again investigated this question, ' 
and answered it in the same sense. Gay also (1891) has proved 
by means of cultures the independence both of Plewrococcus and of 
other forms. Nevertheless, the old idea of a far-reaching poly- 
morphism among the algae is constantly reappearing. 
Since Hansgirg in 1885 came to the conclusion that all possible 
aleae are forms of a single species, and thus showed himself as 
uncritical as Kiitzing before him (¢f. my criticism, Botanische 
Zeitung, 1886), Chodat, and especially Borzi, have quite recently 
announced the genetic connection of many algae which were 
hitherto considered independent. Both workers have tried to give 
greater weight to their opinions by means of evidence obtained from 
culture experiments. To what an extent Borzi is dominated by the 
idea of polymorphism is shown in his most recent work (1895) by 
the treatment of the life cycle of’ Protoderma viride,” to which he 
assigns species of the following genera: Protococcus, Botryococcus, 
Chlorococeus, Limnodictyon, Physodictyon, Palmella, Tetraspora, 
Nephrocytium, Trochiscia, Oocystis, Scenedesmus, Raphidium. The 
connection of all these forms Borzi thinks he has proved by means 
of cultures. According to the view of this worker, the various 
developmental states have “stadii anamorfici”; thus, for instance, 
the Raphidium- and Scenedesmus-forms have the power under 
certain circumstances of remaining and multiplying as such for 
years, and then when opportunity offers they again turn into the 
higher forms. 
Chodat does not go nearly so far as Borzi in his belief in 
polymorphism, and he expresses himself less clearly and distinctly. 
He contents himself with believing (1893-4-5) that such an alga as 
for instance Raphidium, is very variable, so that it may take on the 
form of a Scenedesmus, a Protococcus, a Characiwm, a Dactylococcus, 
or a Sciadium. The Scenedesmus behaves under certain circum- 
