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3. On the Structure and Economy of Tethea, and on an 

 undescribed species from the Spitzbergen Seas. By 

 Professor Goodsir. 



The author, after a brief summary of the observations of Donati, 

 M. Edwards, Forbes, Johnston, and Huxley, on various species of 

 Tethea, described the structure, and deduced the probable economy 

 of a large species apparently undescribed, some specimens of which 

 he had procured from the Spitzbergen Seas. 



The following peculiarities of form and structure were minutely 

 detailed and illustrated : — 



1 . The turbinated form of the sponge. 



2. The partial distribution of the rind. 



3. The minute pores of the rind, arranged in threes ; a pore in 

 each of the angles, formed by the primary branches of the six- 

 radiate spicula. 



4. The water, instead of passing out by oscula, drains through a 

 perforated or net-work membrane which lines a number of irregu- 

 larly tortuous grooves on the surface of the attached hemisphere of the 

 sponge,. — the grooves being continuous with deep fissures, which ex- 

 tend into the rind, and are apparently the result of distension from 

 internal growth. 



5. The silicious spicula are arranged according to the type of the 

 skeleton in the other Tethese. Elongated, slightly bent or twisted rod- 

 like spicula, are combined in bundles by means of fibrous substance, 

 and a few boomerang-shaped spicula, laid crossways. These bundles 

 are arranged irregularly in the centre of the sponge, so as to form a 

 nucleus from which radiating masses extend outwards to the rind, or 

 beyond the surface, where the rind is deficient. The spicula of the 

 rind are large and six-radiate. Their shafts are deeply and firndy in- 

 serted into the radiating bundles. Their three primary branches are 

 set at angles of 120° to the shaft, and to one another. The two 

 secondary branches at the extremity of each primary branch are long- 

 pointed, slightly concave towards the centre of the sponge, and set 

 at an angle of 90° to one another. 



6. The fleshy mass which envelopes the spicular bundles in the 

 interior of the sponge, consists of — 1. Ordinary sponge particles ; 2. 

 Caudate particles, probably similar to the spermatozoa described and 

 figured by Mr Huxley in an Australian Tethea ; 3. Ova-like masses, 



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