SYNCRYPTA SPONGIARUM. 307 



In Urban's interesting paper (1910 c, p. 42) he describes red algse living 

 symbiotically in Clathrina at Naples *. In the mesoglcea he finds round red 

 cells, 7 /J, in diameter, giving rise by binary fission to ellipsoid cells 5 fi by 4^, 

 which become separate spherical cells like the parent. After solution of the 

 red pigment by distilled water, the cells are green. 



It appears possible that the "Sperrnaklumpen" drawn by Vosmaer (1887, 

 pi. 29) may be a further stage in the life-history of these cells of Urban. 

 Scaling Vosmaer's fig. 4 roughly from the collar-cells, the diameter of his 

 sphere is about 14: fi, or rather less if we allow for preservation in absolute 

 alcohol |. As briefly mentioned (ante, p. 300), I observed a number of similar 

 bodies in Clathrina clathrus at Naples (Jan. 3rd). Examined fiesh under 

 the microscope in hematoxylin, they stained strongly and readily before any 

 of the other tissues ; a sphere of about 32 cells was drawn (fig. D) t ;IS we U 

 as one which may have been the 16-cell stage (fig. 0). In the latter the 

 external diameter was measured to be 11 fi and the diameter of the stained 

 spherules l'7yu,: in the former the external diameter was 8 /j, and the 

 diameter of the spherules 1*2 fi. It will be seen that whether or not these 

 resulted from Urban's symbiont, they, as well as Vosmaer's sperm-ball, show 

 no difference from the Syncrypta spongiarum of G. compressa ; and Vosmaer's 

 observation (I.e. fig. 5), that a sphere of presumably 16 cells was enclosed in 

 the tissues of the sponge, suggests that they are derived from the multipli- 

 cation of cells in the mesoglcea, such as is described by Urban. 



" Yellow bodies " were found by Dendy in his Leucosolenia gardineri — a 

 clathrinid fiom 10 to 14 fathoms depth in the (Jhagos Archipelago and 

 "closely related to ... . Leucosolenia (Clathrina) coriacea" (1913, p. 5). 

 He writes (p. 6) : — " The idea that the yellow bodies may be symbiotic algse 

 also naturally suggests itself, but their chemical reactions and the fact that 

 they contain no nuclei appear to me fatal to this view." It is remarkable, 

 however, that the size of these yellow bodies (" '004 to '006 mm. in diameter," 

 p. 4) is that of the bodies identified as symbiotic algse by Urban, who also 

 figures them as uniformly punctated circles in his diagram of a section ; 



* I will preclude at once the natural conjecture that the red varieties of " Ascetta pri- 

 mordialis" (Guancha coriacea), described by Minchin, 1892 c, p. 16, and myself at Naples, 

 are due to the same cause. The colour in these cases is due to the granules in the porocytes 

 and other ectocytes, of which I have given a description (1892 b, p. 482). 



t 1 have measured this on the original drawing, which my regretted friend Professor 

 Vosmaer gave me in 1888. In Bronn's plate the size of the sperm-ball is slightly 

 exaggerated, and a definite circular outline is added, not shown in the pencil drawing, in 

 which the shaded outline is somewhat polygonal. 



X There is a curious hilus shown near the bottom of this figure ; I do not know if this is 

 the ''blank space" to which Hartog refers (1900, p. 127) as in T'olvo.v marking the original 

 lip of the plate of cells which has bent into a sphere. (Fig. H after Dendy corroborates this 

 view.) It suggests also the " slight thickening in the enveloping membrane " observed by 

 Polejaeff in the " sperniospore " of Leucosolenia poterium (1883, p. 33). 



