TETRAXONIDA. 3 



tliice-fourtli.s of the body. The surlace of the oseiihu- ;coue is smooth and irlistenino- 

 .and with faintly marked longitudinal ridges ; whereas that of the poral zone has more 

 prominent ridges, and a punctate appearance due to the pores in the grooves between the 

 ridges ; this appearance is l)rought into relief by drying the sponge, for then the poral 

 .sieves contract and the points of the palisades of cortical oxeas prick up the dermal 

 membrane ; these palisades ai'e not present in the oscular area, which, in tact, is devoid 

 of a cortical skeleton of spicules, though it possesses a fibrous cortex. 



The OSCUles are small circular orifices about 0"75 mm. in diameter, five or six in 

 iiuniber, arranged in an irregular circle on the broad upper end of the sponge. In the 

 complete state they each have an (^uter fringe of protriaenes about 4 • 5 mm. liigh, and 

 an inner fringe of trichodal protriaenes, a little below which is a sphincter. 



The dermal pores occur as sieve-like groups in the more or less longitudinal 

 grooves (VI 11. i!, :i) l)etween the palisades of corneal oxeas, the meshes of the sieves 

 being supported by fan-like tufts of trichodal protriaenes. 



The EctOSOme. The sponge cuts easily, and a vertical section shows the skeletal 

 fibres radiating from a central nucleus. No well-defined boundary is visible to the 

 naked eye between ectosome and choanosome. In the poral zone (VIII. 3 and IX. 15) 

 the pores lead into sub-dermal spaces bounded by vertical rows of cortical oxeas ; the 

 rows of cortical oxeas are likewise present at the base of the sponge in the root-tuft 

 zone. In the oscular zone (IX. 16) there is an ill-defined layer, about 1*5 mm. thick, 

 composed of loose bundles of fibrous tissue crossing in various directions with rounded 

 collencytes scattered about ; also there may be a few scattered oxeas. 



The Canal System. The sulidermal spaces beneath the sieve-groups of pores 

 open into canals descending into the choanosome. The pyriform flagellated chambers, 

 47 X 42 /x. (VIII. 4), are eurypylous ; the figure shows several chambers opening 

 direct into a terminal exhalant canal. 



The chamber system of Cramella simillima Bk. and of other species of Craniella, 

 described by Sollas in his ' Challenger ' Report, is aphodal (21. p. 30, PI. II., fig. 19). 



The Skeleton. A tangential surface section in the poral region shows best the 

 cortical oxeas, which are mostly arranged in double rows, each row bending outwards 

 slightly towards a row of another doul)le series, so as to form an incomplete arch over 

 a sub-dermal space or channel. 



A small " silica pearl " was found in one section. 



Numerous large ova occur, with oval body and thick pseudopodia-like extensions, 

 the liody being 130 X "GS/i, and the total diameter over 300 yu. In some instances, 

 the ova are more rounded and compact, with the cytoplasm more drawn together. 



I had described the specimens as representatives of a new species, Ijut I now find 

 that they l)elong to Craniella mgitla (Lendenfeld). 



Dr. V. Lendenfeld very kindly sent me the revised proofs of his Report 

 " Tetraxonia der deutschen Siidpolar-Expedition, 1901-1903," thus enabling me to 

 make the necessary alterations beff)re it was too late. 



