528 Annals of the South African Museum. 



occasionally a very faint stratification was seen. In the normal septa 

 the processes gradually taper from without inwards (Fie;. 15, D, H ), 

 but very often they are irregularly thickened, certain parts, which 

 stand out as knobs or beads, beint>- thicker than the rest. 



The question may be raised whether this Sphaercplea is really sep- 

 tate in the true sense of the word, and whether the apparent septa are 

 not merely transverse groups of strengthening bars, analogous to the 

 " cellulose-strands " of Caulerpa. Some evidence has been produced 

 above to show that, normally, the " septa " are probably not closed, 

 and their mode of formation is certainly not comparable to that usually 

 found in filamentous Algae. The diverse abnormal conditions 

 also lend countenance to the view that we are not dealing with real 

 septa. 



The often marked inflation of the cells beyond the "septa" (cf. 

 the table below) is probably an indication of the existence, in the 

 living Alga, of a considerable osmotic pressure, to which the thin 

 longitudinal walls would readily respond. The constricted septa 

 appear as so many points of strengthening, preventing an undue 

 inflation of the coenocyte. An investigation of fresh material would, 

 how r ever, be necessary to establish the correctness of this view. 



Table of Dimensions of Vegetative " Cells" of S. africana. 



(Dimensions in //.) 

 Width at middle . (30 66 66 60 78 65 45 -18 51 42 15 45 



Width at septum . 33 45 30 54 51 36 27 36 19 



It is obvious from Heinricher's (Zur Kenntn. d. Algengatt. 

 Sphaeroplea, Ber. Deutsch. But, (les., i, 1883, p. 433 et se^Tab. XII) 

 account that similar conditions obtain also in 8. annulina (lor. cit., 

 pp. 434, 435). Here, how r ever, there appear to be no constrictions at 

 the septa, and I can find no exact evidence in Heinricher's paper that 

 the latter are produced by a number of separate processes. A 



Fig. 16. — SphaeroiAea africana, n. sp. A. A particularly elongated 

 oogonium, with numerous oospheres (o.). B. Oospores in various 

 stages of development. ". In surface-view, showing the broad, 

 crinkled wing ; b, in side-view ; c, quadrangular ; d, triangular oospore ; 

 -?', young oospore, showing the mode of development within the 

 thin membrane first formed. w. Wing. C. Small part of an 

 oogonium, with a number of mature oospores in surface- and side-view. 

 "l<. One of the apertures in the wall of the oogonium. l>. Small part 

 of an oogonium, showing an aperture (op.) in surface-view. E,F,G, 

 and H. Various kinds of abnormal septa, cf. the text. J. Small part 

 of a filament, showing the abnormal formation of a very short cell (s). 

 Figs. A and J x 140, the remainder < 600. 



