FRESHWATER ALG.-E OF THE SOUTH ORKNEYS. 115 



of an inverted funnel ("verkehrt trichterformiger Raum") at the front end of the 

 cell. This, I believe, coincides with the colourless area beneath the beak in the cells 

 of the yellow snow form, although my material was not sufficiently well preserved to 

 enable me to make out its exact shape. Apart from this, however, the Antarctic form 

 agrees also in other respects with the descriptions of A. Braun, Chodat, and Wille. 

 Chodat's fig. 53, B (Algu.es vertes de la Suisse) very much resembles the normal colonies 

 above described, although all the cells were generally not as spherical as his figure 

 shows them. 1 His fig. 53, D (cf. also Wille, in Engler-Prantl, loc. cit., fig. 5, D) shows 

 a similar subdivision of the cell-contents into a number of small parts, as in text 

 fig. 1, G (p. 122) ; in my material, however, the membrane of the mother-cell always 

 remained intact till division was complete, 2 and the Schizochla/mys-like stages figured 

 and described by Chodat were not observed. The most noticeable points of difference 

 between the yellow snow form and Braun's and Wille's Glceococcus lie in the small 

 size of the colonies and possibly in the shortness of the cilia, which are stated to be 

 very long in the latter form, although those which I believe to have observed were 

 invariably rather short. 



There can be no doubt that the three types of colonies found in the yellow snow 

 material and above described belong to one and the same form, as numerous connecting- 

 links were observed. Rather rarely isolated cells of the Chlamydomonas-type were 

 met with in the material ; some of these certainly belong to species of Chlamydomonas 

 (cf. p. 118), but others may well be single swarmers of the Sphterocystis-colomes. 

 Occasionally one finds more or less rounded granular cells with a wide envelope of 

 delicate mucilage around the very delicate cell- wall ; these cells agree in all respects 

 with those of a normal colony, and it seems very probable that such stages constitute 

 the commencement of a new colony. I have, however, been unable to demonstrate 

 cilia in these cells. 



The chief differences between Sphserocystis schroeteri, Chod., and Glceococcus 

 mucosus, A. Br., on the one hand, and the yellow snow form on the other, may be 

 summarised as follows: (1) The colonies of the latter are frecpaently rather more 

 irregular in shape than those of the former ; (2) the cilia, if present, are much shorter; 



(3) the cells are of somewhat smaller dimensions and more frequently oval in shape ; 



(4) Sehizochlamys-]\ke stages have not been observed ; (5) the storage of fat. As I 

 cannot feel certain of the occurrence of cilia in the yellow snow form, it will be best 

 referred for the present to 8ph&rocystis schroeteri, Chod., as a forma nivalis* It is 

 of considerable interest that so abundant a plankton-form as Sphserocystis should form 

 an important constituent of the yellow snow flora. 



1 An oval cell is, however, shown in the lower part of the colony. 



- In one or two cases the membrane of the mother-cell was pronouncedly thickened, appearing gelatinous 

 and stratified. 

 3 Cf. p. 123. 



