R. W. H. ROW—REPORT ON THE SPONGES: NON-CALCAREA. 309 
rarely possess more than 5 or 6, while in the deeper parts of the sponge there 
may be 20 or 25 rows of spicules in each fibre. 
In addition to the spicular fibres, there also occur considerable numbers of 
scattered spicules throughout the sponge. They are exactly similar to those 
found in the fibres. 
There is no special cortical skeleton. 
Spteules. 
A. Megascleres. 
The only megascleres present are tylostyli, which possess well-marked 
heads. The spicule is fairly stout, evlindrical, and the shaft is thickest close 
to the head, from which point it gradually tapers down to a very fine point. 
The spicules are always quite straight. They measure from 0°32 mm. to 
Fig. 18.— Esperella suezza. Microscleres: A x1000; B & C x675. 
0:33 mm. in length and 0:004 mm. in diameter at the thickest point in the 
shaft. The head, which is oval, measures 0°005 mm. in diameter. 
B. Microscleres. (Text-fig. 18.) 
(i.) Chele. (Text-fig. 18, A.) 
The palmate anisochele are very abundant, occurring in large numbers 
throughout the sponge. They do not form rosettes. They are not very 
large, and the length of the largest specimens does not exceed 0:04 mm. 
Small forms are very numerous indeed. 
Gi.) Sigmata. (Text-fig. 18, B.) 
The sigmata are large, and are present in the sponge in enormous numbers, 
so that in some places they almost form a solid mass. For the most part they 
are C-shaped, but occasionally specimens may be seen contort. The average 
length of the sigmata, measuring across the curve, and not along it, is 
0:07 mm., and the diameter of the spicule 0-004 mm. 
Sigmata are occasionally found in which one of the ends is malformed, 
either swollen, or knobby, or possessing one or more excrescences or rays 
upon it. Typical examples are shown in the text-figure. 
