252 PROTOZOOLOGY 



during their life cycle, which perhaps suggests their origin in flagel- 

 lated organisms. In fact, in the chrysomonad Myxochrysis (p. 261), 

 Pascher (1917) finds a multinucleate and chromatophore-bearing 

 organism (Fig. 105, e-j) that stands intermediate between Chryso- 

 monadina and Mycetozoa. Thus there are a number of morpho- 

 logical, developmental, and physiological observations which sug- 

 gest the flagellate origin of various Sarcodina. 



The Sporozoa appear to be equally polyphyletic. The Telosporidia 

 contain three groups in which flagellated microgametes occur, which 

 suggests their derivation from flagellated organisms. Leger and 

 Duboscq even considered them to have arisen from Bodonidae (p. 

 362) on the basis of flagellar arrangement. Obviously Gregarinida 

 are the most primitive of the three groups. The occurrence of such a 

 form as Selenococcidium (p. 572), would indicate the gregarine- 

 origin of the Coccidia and the members of Haemogregarinidae (p. 

 592) suggest the probable origin of the Haemosporidia in the Coc- 

 cidia. The Cnidosporidia are characterized by multinucleate tro- 

 phozoites and by the spore in which at least one polar capsule with 

 a coiled filament occurs. Some consider them as having evolved 

 from Mycetozoa-like organisms, because of the similarity in multi- 

 nucleate trophozoites, while others compare the polar filament with 

 the flagellum. It is interesting to note here that the nematocyst, 

 similar to the polar capsule, occurs in certain Dinoflagellata (p. 310) 

 independent of flagella. The life cycle of Acnidosporidia is still in- 

 completely known, but the group may have differentiated from such 

 Sarcodina as Mycetozoa. 



The Ciliata and Suctoria are distinctly separated from the other 

 groups. They possess the most complex body organization seen 

 among Protozoa. All ciliates possess cilia or cirri which differ from 

 flagella essentially only in size. Apparently Protociliata and Eucili- 

 ata have different origins, as judged by their morphological and 

 physiological differences. It is probable that Protociliata arose from 

 forms which gave rise to Hypermastigina. Among Euciliata, one 

 finds such forms as Coleps, Urotricha, Plagiocampa, Microregma, 

 Trimyema, Anophrys, etc., which have, in addition to numerous 

 cilia, a long flagellum-like process at the posterior end, and Ileonema 

 that possesses an anterior vibratile flagellum and numerous cilia, 

 which also indicates flagellated organisms as their ancestors. It is 

 reasonable to assume that Holotricha are the most primitive ciliates 

 from which Spirotricha, Chonotricha, and Peritricha evolved. The 

 Suctoria are obviously very closely related to Ciliata and most prob- 

 ably arose from ciliated ancestors by loss of cilia during adult stage 



