FRESHWATER ALGJE OF THE SOUTH ORKNEYS. Ill 



prolongent vers les cxtrdmites en arete saillante," according to Chodat, p. 140; "An 

 beiden Enden des Zellinhalts finden sich Vorspriinge . . . sicherlich nur dadurch 

 entstanden, dass die Rippen dor Membran etwas vorsprangen," according to Wille, pp. 

 1G9, 170; cf. also my fig. 23), and, lastly, the apparent formation of new individuals 

 by subdivision of the cell-contents. 1 



(/) CHODATELLA BREVISPINA, n. sp. (PI. I., figs. 25, 26; PI. II., phots. 3, 5, Ch). 



A very typical and rather abundant member 2 of the yellow snow flora is constituted by 

 spiny ellipsoidal cells, which appear to belong to a new species of Chodatella, which may 

 be styled C. brevispina (PL I., figs. 25, 26). The cells of this species are discoid and 

 about 18 M long and 12 M broad, and are covered all over their surface with uniformly 

 distributed spines. The latter are very short and, as a general rule, do not project beyond 

 the surface for a distance greater than twice the thickness of the wall ; they are mostly 

 rather delicate, but occasionally individuals bearing coarser spines were to be found. 

 All the spines on a given cell are generally of about the same length, although some- 

 times slight differences are noticeable. The cell-membrane is colourless, and consists of 

 two well-marked portions, a dark-looking outer (probably cuticular) layer and an inner 

 much lighter layer. There appears to be a single chloroplast, although I do not feel 

 certain of this ; a pyrenoid was not observed. Large quantities of fat are almost 

 always present in these cells. In the majority of cases two more or less rounded 

 masses are found, one at each end of the cell and separated by a central mass of granular 

 protoplasm in which a considerable amount of starch frequently occurs (PI. I., fig. 26). 

 Often one of these two fat-masses is considerably larger than the other, and occasionally 

 only one large mass is present at one end of the cell. In some individuals, lastly, the fat 

 predominates to such an extent that only a small amount of granular protoplasm can be 

 distinguished, all the remaining part of the contents being obscured by the accumulation 

 of fat (PI. I., fig. 25). 



The greatest difficulty in the way of a satisfactory determination of this form as a 

 species of Chodatella lies in the absence of all reproductive stages. In CJiodateUa* 

 reproduction is effected by subdivision of the cell-contents to form a number of new 



1 Wille (Inc. n't., p. 171) also suggests on the basis of his observations that it may become necessary to remove 

 /'. niralis from the genus Pteromonas ; this is based on his view that the ordinary winged cells are aplanospores 

 (re.-, ting- cells), that reproduction is effected by small fusiform zoospores, and on the possibility of the cells containing 

 several chloroplasts without pyrenoids (see loc. cit., p. 169). It does not appear that the last of these observations is 

 correct ; the others have already been criticised above". 



Wille suggests that the oval cells provided with longitudinal ridges, referred to by Lagerlieim as having been 

 found in red snow from Amsterdamo (Spitsbergen) (</. footnote 1 on p. 109), were individuals of P. nivalis. As stated 

 in the footnote on p. 109, I am of opinion that they may belong to the genus Scotiella, but it hardly seems likely 

 Iliat they represent P. niralis. The rather vague description points more to a form like Kcutii.ila polijfitcra. 



Until we know more about llir movement referred to by Chodat, it seems advisable to leave P. nirali.i in its 

 present genus. 



- This form is much commoner than ,sVn( /.//</ union-H^i, but owing to its smaller size not nearly so striking. 



3 E. Lemmermaun, " Beitr. /.. Keuiitn. d. Plaiiktonalgen," I., llf/ln-iijin, xxxvii., 1898, p. 309. Chodat, loc. fit., p. l!ll. 



