46 THE SPONGES. 



show a constant difference between the piniili of the two surfaces. In the 

 other specimens the dermal pinuli have distal rays which are slightly 

 shorter and thicker than those of the gastral pinuli. Measurements show that 

 this relative difference hettveen dermal and gastral pinnli exists, although in some 

 specimens both kinds of pinuli arc perceptibly stouter than in others. Thus in a 

 number of specimens the gastral pinuli were like the one shown in Fig. 10, 

 Plate 4, where the distal ray is so slightly swollen in the middle as to be 

 almost cylindrical in outline. In the same specimens the dermal pinuli 

 were like the one shown in Fig. 7, Plate 4, where the distal ray is suffi- 

 ciently swollen in the middle for the outline to be distinctly fusiform. In 

 other specimens the gastral pinuli were quite as stout and fusiform as 

 Fig. 7, Plate 4, and the dermal pinuli still somewhat stouter and more 

 fusiform. Thus while the individual sponges differ among themselves, 

 within narrow limits, to be sure, in respect to the precise shape of the distal 

 ray, the relative difference between the two surfaces is usually maintained. 

 This generalization is illustrated by the following tabular statement, show- 

 ing the common range of variation among the spicules of two individuals, 

 the one with pinuli as slender as in any of the specimens, and the other 

 with pinuli as thick as in any of the specimens. 



Distal Ray of Dermal Pinule. Distal Ray of Gastral Pinule. 



Length. Greatest Thickness. Length. Greatest Thickness. 



1. Sponge with slender pinules, 240-320 /* 36-40 /* 260-360/1 32-36 /* 



2. Sponge with stout pinules, 210-240 /* 44-56 /i 280-320 /i 36-40/1 



On both surfaces the following uncommon types of pinuli make their 

 appearance. In one type, Fig. 8, Plate 4, the distal ray is conspicuously 

 shortened but not very swollen. Much less frequent is the type shown in 

 Fig, 1, Plate 4, in which the distal ray is very short and greatly swollen. 

 The latter spicule is similar to the dermal pinuli of C. latiis F. E. Sch. and 

 C. elegans F. E. Sch. 



The general dermal covering of the stalk is in all cases lost, but in one 

 of the specimens some of the pinules on the upper part are preserved. 

 These are smaller than the pinules of the body, the proximal and tangential 

 rays measuring about 80 /a x 6-8 /x, the distal ray about 200 /x x 24 /a. 

 The covering spines on the distal ray are not so closely set as in the 

 pinules of the body. 



The hypodermal and hypogastral pentacts (Fig. 9, Plate 4) are alike. 

 All the rays taper to rounded points, and there is no trace of the 



