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, Stigeoclonium, 

 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 Pleurococcus 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 

 algae are forms of a single species, and thus showed himself as 

 uncritical as Kiitzing before him (cf. my criticism, Botanischc 

 Zcitung, 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, 

 Chlorococcus, Limnodictyon, Physodictyon, Palmella, Tetraspora, 

 Neplirocytium, Trochiscia, Oocystis, Sccnedesmus, 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 Scenedcsmus-iorms ' 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 Sccnedesmus, a Protococcus, a Characium, a Dactylococcus T 

 or a Sciadium. The Sccnedesmus behaves under certain circum- 



