i 1:1 -n\\ AII:U AL(J.+: OK Tin: -Tin ORKVK1 115 



"t" an inverted fiinm-1 ( " \vrkclirt kriebterfbmugtr Raum") at the front end of the 

 (11. Tins, I believe, coincides with the eolourleM area bcneuth the beak in the cell* 

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

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

 agrees also in other respects with tin- <le.scriptions of A. Braun, Chodat, and Wille. 

 Chodat's fig. 5.1, B (Alyueji vertes de la Suisse) very much resembles the normal colonies 

 alx>ve descried, although all tin- Us were gem-rally not as spherical as his figure 

 shows tin-in. 1 His fig. B ' also Wille, in Englcr-Prantl, /<*-. cit., fig. 5, D) shows 



a -iinilar sulxlivision of the cell-contents into a number of small parts, as in text 

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

 ivmaineil intact till division was complete,* and the N. /,/:,.. ///'///n/s-like stages figured 

 and described i.y Chodat were not observed. The most notii-ealilt- points of difference 

 between the yellow snow form and Braun's ami Wille'.s (ihrococcus 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 lelieve 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 !>elong to one ami the same form, as numerous connecting- 

 links were observed. Rather rarely isolated cells of the CMamydomon<U-typ were 

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

 p. 118), but others may well be single swarmers of the Sphjerocystis-dAomes. 

 Occasionally one finds more or less rounded granular cells with a wide euvelo]>c 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 Spharocystis schroeteri, Chod., and GVoMOOMMf 

 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 frequently rather more 

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



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



(4) Schizochlamys -like stages have uot 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 Sphwrwysti* S./M ../,//. ('hod., as a forma nivali*.* It i 

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

 an important constituent of the yellow snow flora. 



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



1 In one ur two eves the membrane of the mother-cell wat pronouncedly thickened, appearing gelatinous 

 and stratified. 

 > (/.p. m. 



