PORIFERA OF THE L.M.B.C. DISTRICT. YAS) 
greatest part of which however has been replaced by cys- 
tenchymatous tissue, also called vesicular connective tissue 
or bladder-cells (‘‘ 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 Sezriola, these cells contained 
very little protoplasm which, together with the small 
nucleus, adhered to one side of the cell-wall only, leaving 
the greatest part of the cell quite empty (compare PI. 
Wk fe. 1, Proc. iiipool Biol. Soc., Vol. IID). 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. XIIL., figs. 
1 and 2). Bladder-cells have been already observed by 
various authors in other sponges, as by Vosmaer* in Poly- 
mastia hemispherica, by Sollas + in Pachymatisma, Stryphnus, 
&c., and also in some of the Lithistida. A similar tissue 
is known to occur in many Molluscs and in Tunicata. ¢ 
Of great interest too were strands of spindle-shaped cells 
which occur in great frequency (Pl. XIII., figs. 1—8). 
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 ‘ Willem Barents Expedition, 1880 and 1881,” 
in ‘‘ Bijdragen tot de Dierkunde.” 
+ Sollas, ‘‘ Report on the Tetractinellida,” collected by H.M.S. ‘‘ Chal- 
lenger,” p. XXX1x. 
£ W. A. Herdman, ‘“‘ Report on the Tunicata,”’ collected by H.M.S. ‘: Chal- 
lenger,” Vol. I., pp. 28—29. 
