PORIF'ERA OF THE L.M.B.C. DISTRICT. 225 



greatest part of which however has been replaced by cys- 

 tenchymatous tissue, also called vesicular connective tissue 

 or bladder-cells C' blasiges Bindegewebe " of German 

 authors). These bladder-cells are generally spherical, 

 with an average diameter of 0'04 mm. In the original, less 

 well preserved material of Seiriola, these cells contained 

 very little protoplasm which, together w^ith the small 

 nucleus, adhered to one side of the cell- wall only, leaving 

 the greatest part of the cell quite empty (compare PI. 

 VII., fig. 1, Proc. L'pool Biol. Soc, Vol. III). Also in 

 the second and well preserved material the bladder cells 

 showed eccentrically situated nuclei ; the protoplasm, how- 

 ever, was found not only round the nuclei and along the 

 neighbouring parts of the cell-wall, but threads of it radi- 

 ated throughout the remainder of the cell (PL XIII., figs. 

 1 and 2). Bladder-cells have been already observed by 

 various authors in other sponges, as by Vosmaer * in Fol(/- 

 mastia hemi splicer ica, by Sollas t in Pachijmatisma, Stnjphnus, 

 &c., and also in some of the Lithistida. A similar tissue 

 is known to occur in many Molluscs and in Tmiicata. j 



Of great interest too were strands of spindle-shaped cells 

 which occur in great frequency (PL XIII. , figs. 1 — 3). 

 The cells are arranged longitudinally and in parallel rows, 

 and are apparently imbedded in a clear gelatinous matrix. 

 Their size varies greatly, the largest cells measure about 

 0'048 by 0"014 mm. Both ends of the cells are prolonged 

 into delicate fibres. They are all highly granular, and in- 

 tensely stained after treatment with picro-carmine. The 



* Vosmaer, "Sponges of the ' Willeni Barents Expedition, 1880 and 1881," 

 in " Bijdragen tot de Dierknnde." 



t Sollas, "Report on the Tetractinellida, " collected by H.M.S. "Chal- 

 lenger," p. xxxix. 



X AV. A. Herdman, " Report on the Tunicata," collected by H.M.S. "Chal- 

 lenger," Vol. I., pp. 28—29. 



