On the Occurrence of Gelatinous Spicules. 



321 



"EctyoninEe, and to infer that the Australian species probably belongs to the 

 same sub-family, though perhaps generically distinct. 



Colloscleropkora arenacea n. sp. 



Sponge massive, sessile, solid, with evenly rounded convex upper surface 

 showing parallel sandy tracts, separated by intervening areas with minutely 

 reticulate dermal membrane. Vents small, scattered in intervening areas. 

 Texture incompressible, friable, intensely sandy, the sand being arranged in 

 a lamino-reticulate fashion. 



Megasclcres. — Slender strongyla, straight or nearly so, measuring about 

 0"22 by 0'0025 mm., smooth and with evenly rounded ends. These spicules 

 are very numerous, occurring chiefly in loose wisps radiating towards the 

 surface, where they form sparse surface-brushes. There is no other dermal 

 skeleton. 



Microsderes (figs. 1, la). — Colloscleres of varying form. When contracted, 

 always with an indentation or notch on one side ; sausage-shaped, boomerang- 

 shaped and kidney-shaped. These spicules swell up and become gelatinous 

 on addition of water (figs. 2a ; 3, b, c). 



The single specimen was dredged by Mr. J. Bracebridge Wilson in the 

 summer of 1888-9 at Station 1, near Port Phillip Heads, and is entered as 

 E.N. 923 in my manuscript catalogue, from which the above details as to 

 external characters are taken. 



DESCRIPTION OF PLATE 11. 



Colloscleropkora arenacea n. gen. et sp. 



Pig. 1. — Colloscleres in the contracted state, as seen in an old Canada balsam preparation, 

 unstained, x 460. 



Fig. la. — Two contracted colloscleres from the same preparation, approaching isochelue 

 in form, x 460. 



Pig. 2. — A collosclere enclosed in its vesicle, separated in absolute alcohol, x 480. 

 Pig. 2a. — The same collosclere after swelling up in water, x 480. 



Fig. 3. — A scleroblast (a) and" two colloscleres (b and c) examined in water, unstained. 

 The colloscleres have swollen but the secretion-knob on the scleroblast has not ; 

 b', the same collosclere as represented in b, after running in a drop of fuming 

 hydrochloric acid from the edge of the cover-glass, x 480. 



Fig. 4.-A group of scleroblasts surrounded by mesoglcea ; from a teased preparation, 

 very lightly stained with paracarmine and mounted in Canada balsam. The four 

 upper cells show the nucleus very distinctly ; the lowest one is focussed on the cell- 

 membrane and shows a secretion-knob, x 480. 



Fig. 5. — A group of scleroblasts in the mesogloea, with associated colloscleres and vesicles. 

 From a teased preparation stained with paracarmine and mounted in Canada 

 balsam, x 480. 



