CHAPTER XI. 



SPECIAL MORPHOLOGY AND TAXONOMY OF THE 

 MASTIGOPHORA. 



The classification of Protozoa was first put on a modern basis 

 by Biitschli (1882 L888). By this time larval forms of various 

 groups of invertebrates, worms, entomostraca, rotifers, desmids and 

 diatoms, all of which had been included in the Leeuwenhoek group 

 of Animalcula, were properly classified, and the Protozoa were 

 limited to the forms which we know today. For general purposes 

 there has not been much improvement over Biitschli 's system 

 whereby the Protozoa were divided into four main groups: (1) 

 The Sarcodina, in recognition of Dujardin's pioneer work on the 

 living substance of rhizopods; (2) the Mastigophora, a term sug- 

 gested by Diesing (1865) for Dujardin's group les flagelles; (3) the 

 Infusoria, a term connoting the original Infusionsthiere, and Leden- 

 miiller's term Infusoria, and Dujardin's les ciliees; and (4) the 

 Sporozoa, a term introduced by Leuckart (1879) for strictly parasitic- 

 types of gregarines, and coccidia. 



The majority of recent workers have followed Doflein (1901) in 

 dividing the phylum Protozoa into two unequal groups or sub- 

 phyla: (1) The Plasmodroma, including Mastigophora, Sarcodina 

 and Sporozoa; and (2) the Ciliophora, including Ciliata and Suc- 

 toria. The writer fails to see any advantage in the creation of these 

 sub-phyla, although the Infusoria differ from other Protozoa, not 

 only in having dimorphic nuclei and fertilization by conjugation, 

 but also in the possession of the most highly differentiated cortex 

 to be found in the entire group of Protista. The absence of di- 

 morphic nuclei in some groups (Opalinidae), the occurrence of 

 fertilization by copulation of gametes (Glaucoma, Opalinidae) and 

 the interpretation of conjugation as evidence of an ancestral brood 

 of gametes indicate that in these respects the Infusoria fall in line 

 with other Protozoa. 



A second change introduced by Doflein (1901) was to divide the 

 Sporozoa into two sub-phyla — Cnidosporidia and Sporozoa, s.str., 

 the former including Myxosporidia, Microsporidia, Sarcosporidia 

 and Actinomyxida; the latter gregarines, coccidia and hemosporidia. 

 This change has much to recommend it and is adopted in the present 

 work. Other, but minor, changes from the classification as given 

 in the first edition of the present work will be found in each of the 



