32 GUIDE TO THE CORAL GALLERY. 



MON AXON IDA (MONAXON SpONGES). 



High Cases T^jg Order contains by far the laro:est nnmber of species. The 



IV -VI • • 



skeleton-spicnles are uniaxial, i.e., shaped like rods, like needles 



pointed at one or both ends, or like pins ; six-rayed and four -rayed 

 spicules never occur. The spicules may be scattered or united into 

 bundles, and may form radiating or reticulate scaffoldings. Flesh- 

 spicules may or may not be present, one of the most common forms 

 being buckle-shaped (Fig. 17). The huge Neptune's Cup Sponges, 

 Poterion 'patera (on pedestals), from the East Indies, are among the 

 largest of Sponge forms ; the skeleton is composed of a dense net- 

 work of bundles of pin-shaped spicules. 



The large specimen of Poterion. placed above the Hexactinellid 

 Case, and formed of three trays one above the other, belongs to a 

 closely allied species. 



The Boring Sponges, which also have pin-shaped skeleton 

 spicules, are remarkable for their habit of boring into shells and 

 limestone. 



Gliona celata (Case IV. 3) is very common in oyster shells, in 

 which it excavates extensive lobed galleries ; the oscules and groups 

 of pores are situated on conical elevations which project through 

 small holes in the surface of the shell. Vigorous specimens burst 

 through the shell and form large cork-like masses (Case IV. 3), 

 the identity of which with the boring portion was for a long time 

 unsuspected. The magnificent specimen of Caulospongia verticillata 

 (Fig. 1.5 ; Case IV. 2) has a thick main stem branching into three, 

 the stems giving rise to closely-set whorls (or spirals) of thin lamellae 

 gradually diminishing in size from below upwards. 



The massive Suherites icilsoni (Case IV. 3) is remarkable for its 

 brilliant purple colour. The colouring matter forms a rich purple 

 solution in acidified alcohol. Esjwriopsis ciiollengeri (Fig. 16), from 

 82") fathoms, east of Celebes (specimen in fluid, Case IV. 4), one of 

 the " Challenger " treasures, has a main stem giving off along one 

 edge a series of stalked bowl-shaped fronds increasing in size from 

 below upwards. The in-current pores are situated in the concavity, 

 and the minute oscules on the convex surface of each bowl. 



The series of specimens of Echinonema typicum (Case IV. 4) 

 shows well the great variation in form that may occur in one and 

 the same species. 



Fresh-water Sponges (Case VI. 3, facing west) are common 



