OALCARKA. 13 



It i- miliiitimatr that this interesting structure cannot be made out with certainty. 

 Tlic origin of (he lla^cllatcd chambers nor the osculc can lie men clearly ; an isolated 

 group of flagellated cells forms outaide the gastral layer, and over this a few triradiatett 

 tiinl oxea grow (nee Fig. 31i). As the Hagcllated chamber grows it tips up the 

 ii.itcs and oxea, which thus begin to point outward* while they continue to grow 

 (see Fit: -U6). At the oscular end of the sponge therefore the flagellated chambers 

 <1 in it grow as divcrticula of the gastral layer, nor is there any lining of flagellated 

 "IN in this part of the gastral cavity. 



Spicules (Fig. 32). 

 The Oxfa are of one sort : 



(a) Small projecting oxea, slightly irregularly bent, faintly hastate at the 

 thinner end, bluntly pointed at the thicker end. 70 M to 210 M long x CM 

 I- in a thick. 



radiates. The triradiates are of two sorts : 



(c) Alate triradiates from the gastral layer. Basal ray straight, tapering 

 slightly, then pointed ; maximum size 480 M long and 12 M thick. Paired 

 rays unequal, slightly irregularly bent, maximum size 160 M long x 12 M 

 thick. Oral angle 130 to 135. 



((/) Alate triradiates from the tubar skeleton. Boaal ray straight, tapering 

 slightly, then pointed, 100/* to 140ft long x CM to 7 n thick. Paired 

 rays nearly equal, straight, 70 M long x CM to SM thick. Oral angle 120 

 to 130. 



The Quadrirad iales are of one sort : 



(') Alate quadriradiutes from the gastral layer. Banal ray straight, tapering 

 slightly, then bluntly pointed, 320 M to 480 M long x 10 M to 12 M thick. 

 Paired rays unequal, nearly straight, 140 M to 240 M long x 10 M to 12 M 

 thick. Oral angle 130 to 140. Apical ray bluntly pointed, slightly lient 

 orally, 1:50 M to 180 M long, oval in section, SM to liV thick x 1'2 n to 

 16/u deep. In side view the apical rays sometimes appear swollen 

 near the point, the depth being greater than at the junction with the 

 facial rays. 



Oscular spicules : 



(/) Quadriradiates from the oscular edge, Imaal ray straight or slightly bent 

 Inckwards, HO/* to 140 M long x SM thick. Paired rays about equal, 

 bending downwards, bluntly pointed, 80 M to 110M long x 10 M thick. 

 Oral angle 145 to 155. Apical rays short and sharply pointed. 



