SPONGES. KALLMANN. 22' 



"length. Echinating principal styli are of fairly common oc- 

 currence, and are frequently, as also are occasionally the 

 echinating acanthostyles, surrounded over a greater or less 

 portion of their length by a sheath of spongin. Scattered 

 auxiliary spicules are moderately abundant, other interstitial 

 megascleres comparatively scarce. 



A peculiar feature of the skeleton is the occasional occur- 

 rence of short slender fibres, attached at one extremity only. 

 These "semi-detached" or "floating" fibres, which appear to 

 be most frequent in the superficial portion of the skeleton, 

 rarely contain more than two or three (almost invariably uni- 

 serially arranged) spicules and are often reduced to a single 

 spongin-ensheathed spicule. There is accordingly in this 

 species a transition from echinating spicules to "echinating" 

 fibres. 



The dermal skeleton is a layer of crowded auxiliary spicules 

 arranged without order ; in the dry condition it forms a 

 whitish encrustation. 



Megascleres. — 



(i.) Smooth, usually more or less curved, subconical 

 principal styli ranging from about loo to 280 //, 

 though seldom exceeding 230 p, in length ; those of 

 intermediate length are the stoutest, attaining to 9 fi 

 in diameter. 



(ii.) Straight subconical acanthostyli, with very small 

 spines, or with merely rugged surface, ranging in 

 length from about 50 to 100 ji, though rarely exceed- 

 ing a size of 80 x 6 jt. Spicules of length in the 

 neighbourhood of 100 ft graduate in form between 

 principal and accessory styli. 



(iii.) Straight or sometimes slightly curved auxiliary sub- 

 tylostyli or styli ranging in length from probably less 

 than 180 ]i to 350 fi, with a maximum diameter of 

 4.5 >i. The shorter are usually indistinguishable 

 from the slenderer principal styli, and so it is impos- 

 sible to determine the lower limit of their length. 



JMicrosclcres. — 



Slender hair-like toxa, of which the longest observed was 

 210 p in length. They appear to be moderately 

 abundant, but, owing to their tenuity, are visible in 

 situ only with great difficulty. Their normal shape 

 is that shown in the text figure, but departures from 

 this, due to flexion and torsion of the arms, are 

 frequent. 



