MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 257 



Tetrasporidse. Such Palmella-stages are difficult to distinguish from 

 the lower algpe. 



Reproduction is invariably by division, usually and typically 

 by longitudinal division, exceptional transverse division occurring 

 in relatively few forms (O.vyrrhis, Polytoma, Parapolytoma, etc.). 

 In most cases there is a doubling of the characteristic cell organs- 

 nucleus, blepharoplast, parabasal body, flagella, chromatophores, 

 etc., although in some authentic cases the flagella and basal bodies 

 are discarded and new ones are formed (see p. 210). In many cases, 

 also, division does not occur during the motile phase, but only after 

 the flagella are thrown off and the individual goes into a resting 

 phase analogous to the Palmella-stage. Such quiescent individuals 

 form what are called "division cysts" within which reproduction 

 occurs {Eiiglena spirogyra, Euglena gracilis, etc.). 



Sexual processes are well developed in the Phytomonadida, very 

 questionable in Euglenida, and have never Ijeen observed in Chry- 

 somonadida and Cryptomonadida. 



Permanent cysts with resistant walls are known in relatively few 

 forms, and where found they seem to be simpler the more complex 

 the organism and rice versa. The cysts usually contain an excess 

 of reserve foodstuff in the form of oil, starch, paramylum, etc. 



Most of the Phytomastigoda have the ability to secrete gela- 

 tinous substances from the cortex through the pellicle and so to 

 form a gelatinous matrLx in which the cell lies. Upon reproduc- 

 tion many cells are thus enclosed in jelly with, usually, the flagella 

 extending through it to the outside. In this way spheroidal colo- 

 nies are formed in many cases {Syncrypta, Uroglena, Uroglenopsis, 

 Chrysosphcerella, etc.). The secretion of substance (cellulose, gela- 

 tinous, chitinous) from the posterior end of the cell results in the 

 formation of definite stalks. These may or may not be accom- 

 panied by tests or houses which may fit the cell tightly, in which 

 case the test is secreted from the entire periphery of the cell {Chry- 

 sococcvs, Trachelomonas, Dinoflagellata) , or it may be considerably 

 larger than the contained cell, in which case it is first secreted from 

 the cell as a whole and later from only a distal expanded portion as 

 in Dinobryon, Hyalobryon, etc. (Senn). 



The majority of Phytomastigoda are widely distributed in both 

 salt and fresh water. The Coccolithophoridse, Silicoflagellidse and 

 the majority of the Dinoflagellida, are exclusively marine. The 

 Chlamydomonadidse and most of the Volvocidse on the other hand 

 are limited to fresh water. Many of them are decidedly planktonic 

 and clear lakes and water supplies often contain them in such num- 

 bers as to impart distinct colors (red, yellow, green), odors and tastes 

 (especially Symira and Uroglenopsis) to the water. Iron in the 

 water leads to abundant growth of Trachelomonas; nitrogen, to 

 various types of Euglenida and Cryptomonadida. Many of them 

 17 



