114 The Classification of Protozoa 



PROSPECTIVE SOURCES OF 

 TAXONOMIC DATA 



As will be noted in Chapters 4-7, there are still many taxonomic 

 areas in which inadequate information makes disagreements unavoidable. 

 Since it becomes increasingly evident that superficial characteristics form 

 an inadequate foundation for a natural classification of Protozoa, present 

 differences of opinion cannot be reconciled completely until more is 

 known about the morphology, biochemistry, physiology, and life-cycles 

 of many species. Therefore, future progress will depend largely upon the 

 contributions of specialists working in different fields. Such details as 

 the finer structure of flagella, the organization of ciliary patterns and 

 peristomial areas in ciliates, distribution of the various types of chloro- 

 phyll and other pigments in flagellates, the composition of stored foods, 

 the structure of endoplasmic organelles, the organization of nuclei, and 

 the basic details of mitosis should all contribute to the development of 

 a less imperfect taxonomic system. The bearing of biochemical data on 

 taxonomic questions may prove to be very important. The determination 

 of minimal food requirements and the analysis of synthetic potentialities, 

 which are possible for species established in chemically defined bacteria- 

 free media, may yield clues to relationships now obscured by morphologi- 

 cal specializations. Taxonomists may even become concerned with such 

 matters as comparative data on digestive enzymes. For instance, the ob- 

 servation that Amoeba proteus (Chaos diffluens) and Pelomyxa caroUnen- 

 sis (Chaos chaos) are similar in their content of peptidase and catheptic 

 proteinase and are both quite different from Pelomyxa palustris (1), is 

 especially interesting in view of the disputes concerning their generic 

 status. And finally, a more thorough analysis of life-cycles is probably 

 essential for the satisfactory classification of various genera and families 

 whose taxonomic status is uncertain at present. 



THE IDENTIFICATION OF 

 PROTOZOA 



In beginning a study of the Protozoa, the student is often interested 

 in identifying species as they are encountered in the laboratory. Un- 

 fortunately, such identifications are not always easy, and are occasionally 

 impossible with the more readily available library facilities. There is no 

 comprehensive determinative manual for the Protozoa as a whole. Nor 

 is there available a complete manual for any of the four major groups 

 of Protozoa. As a result, the identification of a particular species some- 

 times becomes a problem for the specialist with extensive knowledge of 

 a certain taxonomic group. In some cases, as pointed out by Pringsheim 

 (19), the establishment of pure-line cultures from single organisms may 

 be a desirable, or even an essential step. 



However, the existence of such difficulties does not mean that the 

 student should consider the task of identification a hopeless one. Many 



