164 The Mastigophora 



multinucleate form also has been observed in cultures (123). Either mul- 

 tinucleate stage may produce flagellate buds. A comparable plasmodium 

 has been reported in Euglena gracilis (Fig. 4. 33, N) and Phacits caudata 

 (Fig. 4. 33, O) by Krichenbauer (167); also, in Astasia klehsii. In A. 

 klebsii no fission occurs in the plasmodial stage, which apparently origi- 

 nates as a result of increased osmotic pressure in old cultures. Even a 

 return to a normal medium does not induce fission (57). 



Although the Euglenida are mostly fresh-water flagellates, a number 

 of genera are represented in salt-water and certain fresh-water species 

 have become adapted to sea water under laboratory conditions (82). 

 However, Euglena gracilis grows only in a salt concentration less than 

 that of 40 per cent sea water (185). 



Although it is not difficult to recognize Euglenida, in view of their 

 characteristic features, subdivision of the group into taxonomically sound 

 suborders and families apparently remains a problem for the future. The 

 old three-family system — Euglenidae, Astasiidae, and Peranemidae — was 

 convenient up to a certain point. Green flagellates could be placed in the 

 Euglenidae, and holozoic types, often with a pharyngeal-rod apparatus. 

 could be assigned to the Peranemidae. The residue of colorless flagel- 

 lates could be dropped into the Astasiidae. Various observations have 

 disturbed this taxonomic tranquillity. The discovery of colorless stigma- 

 bearing flagellates (good species of Euglena except for the absence of 

 chromatophores), the recognition of Hyalocephalus as a colorless homo- 

 logue of Phacus, and recent observations on the loss of chlorophyll in 

 Euglena make the presence or absence of chromatophores a feature of 

 doubtful value in separating families. In fact, certain generally recog- 

 nized species of Astasia are possibly nothing more than colorless strains 

 of Euglena (239). Furthermore, Pringsheim and others have observed 

 that growth of Euglena gracilis in darkness, following treatment with 

 streptomycin, induces loss of the stigma after the chromatophores have 

 disappeared. This new creation is a genetically stable strain which would 

 be eliminated automatically from the old family Euglenidae. The old 

 family Peranemidae also is not homogeneous in that a pharyngeal-rod 

 apparatus is present in some genera and not in others, holozoic nutrition 

 has not been demonstrated in certain cases, and differences in flagellar 

 apparatus are well known. 



Hollande (110) has divided the Euglenida into three groups which, in 

 conformity with the present system, would be recognized as suborders — 

 Euglenoidina, Peranemoidina, and Petalomonadoidina. These suborders 

 would be divided into appropriate families as adequate information be- 

 comes available. Although separation of the Peranemoidina and Petalo- 

 monadoidina may not be clear cut, if the siphon of Entosiphon (Fig. 4. 

 37, B) is only a modified rod-apparatus as seen in Peranema (Fig. 4. 36, 



