36 
Transactions of the lloyal Society of South Africa. 
have themselves figured specimens in which the retuse apex is scarcely 
recognisable (cf. also Eaciborski, ' Eozprawy Akacl. Umiej. Krakow,' ser. 2. 
ii, 1892, PI. VI, fig. 20, a), and in sample 327 forms were encountered 
(f. rottmdata, Fig. 11, F) in which the apices were smoothly rounded off 
and without any trace of retuseness (side-view as in Fig. 11, E^h). Such 
specimens might be regarded as not belonging to C. laeve, were it not that 
they are connected with the typical form by transitions ; thus, individuals 
were occasionally met with in which one semicell showed a retuse apex, 
whilst the other was rounded off as in Fig. 11, i^, Numerous specimens 
were, moreover, observed in which the apex was retuse on the one semicell 
but merely slightly thickened on the other (Fig. 11, E, a\ a"). A reference 
to Figs. 11, E, a, a', a", a'" further shows that the shape of the semicells 
(either of one or both) is subject to considerable variation. Tims, the lower 
parts of the sides may be almost subparallel (Fig. 11, E, a, especially the 
lower semicell), the sides may be somewhat angular (as iu Fig. 11, E, a"), 
and the width of the apex rather diverse (cf Fig. 11, E, a, a' , a!', etc.). 
Specimens like those figured in Fig. 11, E, a", lead over to the form of 
C. rectangular e, G-run., shown in Fig. 11, G (especially a'), whilst forms like 
those represented by the lower semicell in Fig. 11, i?, a' , are transitional to 
forms of C. granatum, Breb. {cf. Fig. 11, -H", and p. 32). 
In some few cases individuals Avere observed in which the sides of the 
semicells converged very markedly (f. acuminata, Fig. 11, D) ; in these the 
apex was not retuse, but more or less rounded, and the semicells, in side- 
view (Fig. 11, D, h), were more rounded than was the case with the other 
forms {cf. Fig. 11, E, h). 
It would thus appear that C. laeve, Eabenh., may vary in respect of the 
apex, the punctation of the membrane, and the form of the lateral margins, 
extreme conditions approaching on the one hand to G. granatum, Breb., on 
the other hand to C. rectangulare, Grun. 
13. Cosmarium sjportella, Breb. ; W. & G. S. West, loc. cit., p. 185, PI. 
LXXXII, figs. 12, 13. 
var. simijlex, F. E. Fritsch, nov. var. (Fig. 14). 
Cellulis a fronte visis apice laevi, lenissime convexo vel truncato vel 
lenissime retuso ; a vertice visis late ellipticis, inflatione mediana nulla ; 
membrana cum granulis sparsis non punctulata, sine tumore central!. Long, 
cell., 48-60 fx ; lat. cell., 39-42 /x; lat. isthm., 10-12 /x; crass., 24-26 /x. 
Samples 312, 314, 315. 
This variety, apart from the slightly larger dimensions, differs from the 
type mainly in the absence of the central granulated tumour in front- and 
end-views. Since this tumour is developed to a very variable extent in the 
type itself, it is possible that no sharp limit could be drawn between it and 
the new variety. 
