PHYTOFLAGELLATES 107 



light microscope, but electron microscopy reveals their exquisitely 

 varied detail and has permitted taxonomists to distinguish specific 

 types, both by study of whole detached scales and by preparation 

 of replicas reproducing the contours of intact cell surfaces. Thus 

 for example the delicately scalloped scales of Chrysosphaerella have 

 been studied by Fott and Ludvik (1956a) and Harris and Bradley 

 (1958), the peculiar, bristled, thumb-tack scales of Physomonas 

 (= Paraphysomonas) vestita by Houwink (1952), the ribbed and 

 pitted scales of Synura by Manton (1955a) and the tiny, elegantly 

 sculptured scales of Chrysochromulina by Parke, Manton, and 

 Clarke (1955-1959). Generic revisions are based in part on 

 extensive studies of scale variations in Mallomonas by Asmund 

 (1955, 1959) and Harris and Bradley (1960) and in Synura by 

 Petersen and Hansen (1956, 1958). Deflandre and Fert (1953) 

 and Parke and Adams (1960) have examined the scales of cocco- 

 lithophorid flagellates, a group closely allied to the chrysomonads. 



Additional light on the question of scale structure is provided 

 by the micrographs of sectioned Chrysochromulina (Parke, Manton, 

 and Clarke, 1958, 1959; Manton and Leedale, 1961a) and Para- 

 physomonas (Manton and Leedale, 1961c). In each of the Chryso- 

 chromulina species illustrated in these papers, two kinds of scales 

 occur, differing from each other in size, shape, and sculpturing. 

 In C. ericina some scales are flat two-layered discs and others have 

 enormously long spines. In C. chiton, larger scales are saucer- 

 shaped and smaller ones alternate with them, lying beneath and 

 overlapping the rims of two adjacent saucers. In C. strobilus, the 

 larger scales form a close mosaic over the cell membrane and the 

 smaller scales lie above these. Thus the problems of scale pro- 

 duction and disposition are even more complex than the elaborate 

 patterns of the individual scales might suggest. Production of 

 scales in intracellular vesicles is demonstrated in Paraphysomonas 

 vestita (and also in a green alga, p. 120). 



Usually considered to be the most primitive chrysomonads are 

 the supposedly uniflagellate chromulinids. The basis for this 

 distinction became suspect with the publication of a detailed study 

 of Chromulina psammobia by Rouiller and Faure-Fremiet (1958a) 

 showing the presence of a second flagellum {Chromulina pleiades, 

 examined briefly by Pitelka and Dougherty [unpublished] some 

 years ago, has two equal acroneme flagella [Fig. 35, PI. X]. The 



