24 THE PROTOZOA 



test; Oersted ('73), however, showed that in the lower plants there 

 are forms differing only in the presence or absence of chlorophyl. 

 These forms may be arranged in a series as follows : l 



With chlorophyl Without chlorophyl With chlorophyl Without chlorophyl 



Oscillaria. Beggiatoa. Spirulina. Spirochaeta. 



Leptothrix. Leptomitus. Palmellaceae. Chroococcaceae. 



Chlamydomonas. Chlamydomonas hyalina. Synedra. Synedra putrida. 



A similar series can be arranged among the Protozoa, including 

 forms which cannot be genetically separated, though some contain 

 chlorophyl, and some are colorless. In the first of these, nutrition is 

 holophytic or of the green plant type, in the second saprophytic or of 

 the fungus type. The chlorophyl differential, if used here, would 

 separate closely allied and in other respects identical forms, always to 

 be found among the Mastigophora, and would lead to confusion. 

 Furthermore, the chlorophyl differential would cause confusion in the 

 classification of the fungi, where colorless representatives of several 

 families of the Phycomycetes reproduce by colorless swarm-spores. 

 Again, some of the Mastigophora with chlorophyl are not dependent 

 upon this substance for their nutriment, but may combine the plant 

 type with the animal type of food-getting (e.g. Chromnlina and some 

 Dinoflagellidia, Fig. 4). 



Stein sought a differential in the presence of contractile vacuoles 

 and of nuclei, which, he maintained, are not found in vegetable swarm- 

 spores, but are characteristic of all animal cells. This view has not 

 been supported by later discoveries, for not only have vegetable spores 

 been found to possess nuclei, but many of them are also provided with 

 contractile vacuoles. 



Haeckel bases the classification of animals and plants upon nutri- 

 tion, which differs but little from the earlier chlorophyl differential. 

 All forms with the power of absorbing carbon dioxide, water, and 

 nitrogen compounds, and of combining them into proteids, he calls 

 plants, those without this power, animals, but he considers that this 

 division, though logical, is at best only artificial, and gives no clue to the 

 actual phylogenetic relations of Protozoa and Protophyta. As a single 

 differential, however, the method of nutrition is probably as satisfac- 

 tory as any, for there are only a few forms which combine the two 

 modes of food-getting. If rigorously applied, however, it cannot fail 

 to shock the prejudices of both botanists and zoologists in claiming for 

 the animal kingdom forms which have usually been identified with the 

 vegetable kingdom, and vice versa. Although Haeckel states that the 

 dividing line is purely arbitrary and does not represent genetic affinity 



iSee Entz ('88). 



