1915.| N. ANNANDALE: Indian Boring Sponges. KE 
ferous lobes through which tylostyle spicules project upwards and 
outwards (pl. i, figs. 2, 3, 4). In profile these papillae, with 
their supporting tubule, are trumpet-shaped. Their outer walls 
(pl. i, fig. 4) are coated with minute calcareous particles con- 
siderably smaller than those which lie scattered in the interior of 
the sponge and on the poriferous papillae. They are covered by 
a delicate cortex, which protects the calcareous particles against 
strong acid unless the surface is subjected to its action for a con- 
siderable period. The mixed and the poriferous tubules are about 
equally abundant. 
Skeleton.—In the chambers the macroscleres lie scattered, 
irregularly and somewhat sparsely, parallel to the outer walls. As 
a tule they are more abundant in the upper than in the lower parts. 
Occasionally they seem to radiate from the chambers into the con- 
necting tubules, but this arrangement is never of a very regular 
nature and no trace of it can often be detected. In the vertical 
tubules the macroscleres form supporting columns, their heads rest- 
ing in a more or less complete, and more or less regular, ring at the 
base of the tubule and their points directed upwards. In the case of 
the mixed papillae the heads are rarely on anything like a uniform 
level and the points project outwards as well as upwards. The 
ordinary (%.e. the smaller) microscleres lie scattered, somewhat 
sparsely and almost uniformly, throughout the sponge, but their 
main axis is always approximately parallel to the outer surface. 
The gemmules have a special skeleton, which is described below. 
Spicules.— The macroscleres are small, slender tylostyles, as a 
tule quite straight, sharply and gradually pointed at one extremity 
and bearing a well-differentiated head at the other. The head is 
most frequently somewhat heart-shaped, but in many cases almost 
spherical and occasionally with a tendency to be trilobed. It con- 
tains as a rule a single minute expansion of the axial tubule of the 
spicule. There is no distinct contraction of the shaft below the 
head but, at about 1/10 the distance between it and the point, the 
shaft is surrounded by a single convex ring. The extent to which 
this ring is developed varies somewhat, but its presence and posi- 
tion seem to be practically constant features of the species. The 
average length of the macroscleres is 0°2 mm., the extremes being 
o°148 and 0°234 mm. 
. The microscleres are all slender spirasters of the normal zig- 
zag type, but they differ greatly in size and two groups may be 
distinguished amongst them in accordance with this character. 
Those of the small type are, when well developed, from o0°008 
mm. to 0°042 mm. in length and have as a rule from 4 to 8 bends, 
but are sometimes irregularly sinuous. Their spines are arranged 
in a regular spiral. These spicules lie scattered throughout the 
sponge. 
The larger microscleres (fig. IA). are as much as 0°126 mm. 
long, or even longer, They have more numerous and as a rule less 
well-defined whorls. The spicules of this type are found only on 
the gemmules. 
