BY E. F. HALLMANN. 433 



prominent parts. The surface is free from cliaracteristic in- 

 equalities, and, in general, is smooth and even; a dermal mem- 

 brane is present, and, though thin, is usually well-defined. The 

 oscular tubes, whose diameter varies from 3 to (rarely) 10 mm., 

 are lined by a stouter and tougher membrane, which also forms 

 numerous diaphragm-like dissepiments stretching across their 

 lumen. Concerning the life-colour, which is known with certainty 

 only in the case of Port Phillip specimens, Dendy states that 

 " orange is the prevailing tint and there are no very great de- 

 viations from this" ; the colour in spirit ranges from dull yellowish- 

 white to a pale brown. Well preserved specimens are of firm, 

 sometimes slightly cartilaginous, moderately tough consistency, 

 and are brittle rather than flexible; but apparently the sponge 

 readily undergoes some amount of maceration, with the result 

 that, as a rule, spirit specimens are comparatively soft, com- 

 pressible, and resilient. The consistency depends to some extent 

 upon the degree of coarseness of the fibres, which is variable. 

 Specimens dried in the ordinary way (without previous removal 

 of the sarcode) are light, open, and somewhat bread-like in 

 texture, and, considering their horny fibrous skeleton, are some- 

 what brittle. The fibrous reticulate skeleton, obtained by treat- 

 ment with caustic potash, presents certain constant features, but, 

 in different specimens, varies greatly in the closeness of its 

 texture and in elasticity, and to some extent also in colour and 

 pattern. A dense irregular network of stouter (primary) fibres 

 bounds each of the oscular tubes, and from this -taking the 

 (simple) case of a separate branch dendritically branching, 

 secondary fibres run out (in a slightly upward direction) to the 

 surface; these secondary fibres, which to within a short distance 

 of their outer extremities are connected together by (usually 

 plexus-forming) cross-fibres, are disposed in such a way that the 

 skeleton, viewed from the exterior, presents a very imperfectly 

 honeycomb-like structure. The colour of the skeleton varies 

 from yellowish-white to golden-yellow, according to the degree of 

 development of spongin. 



As seen in section under the microscope, the skeleton-reticula- 

 tion is of a very irregular pattern, and the fibres are of very 



15 



