476 Records of the Indian Museum. [VoL. XI, 
The fact that a considerable number of small encrusting 
sponges are in the habit of invading and occupying the excava- 
tions of Clionidae to the detriment of the latter is quite clear from 
the foregoing notes, and I have abundant evidence that the para- 
sitic species described form only a very small proportion of the 
sponges of similar habits that exist in Indian seas, more particu- 
larly on the decaying parts of coral reefs. The question naturally 
arises, How do the Clionidae protect themselves? No direct 
observations on this point have been made in the field but in the 
case of Thoosa investigatoris and Coppatias investigatrix the fact 
that the invading sponge was evidently in a comparatively early 
developmental phase enabled some interesting deductions to be 
made. Fig. 1 on pl. xxxiv shows a young sponge of C. tnvestiga- 
trix which has just penetrated into the outer part of a burrow of 
T. investigatoris. ‘The shell has been dissolved away and one sees 
in the lower part of the figure the base of an exhalent papilla 
from below, the middle of the figure is occupied by the Coppatias, 
while in the upper part a confused mass of spicules belonging to 
the Clionid is shown. ‘The invading sponge appears to have made 
its way through an inhalent papilla that has degenerated into a 
mere confused mass; it is shown in the upper part of the figure. 
The Coppatias, however, has not merely penetrated the papilla, 
for it contains small cavities that apparently represent fragments 
of calcareous matter detached by itself. Fragments of precisely 
the same shape and size were observed in situ in preparations in 
which the action of the acid used in extracting them from the 
shell had not gone so far. 
There are several points of interest to be noted in this 
preparation. Firstly, the Clionid has secreted a horny membrane ! 
(h.c.) wherever it is in contact with the invading sponge. Secondly, 
the exhalent papilla (¢.p.) at the base of which the invading sponge 
has entered the shell is distorted and has its armature of macro- 
scleres greatly extended and increased. Thirdly, the inhalent 
papilla through which the Coppatias has apparently* made its way 
is as already stated completely disorganized. Fourthly, the in- 
vader is very minute and forms a compact mass that does not 
spread out over the surface of the shell. 
Fig. 2 represents a later stage in the attack in the same case. 
The Coppatias has penetrated well into the burrows of the Clionid 
and has to some extent adapted itself to their form. The Clionid 
has shrunk considerably in its excavation and has secreted round 
itself a thick horny coat, not merely where it is in actual contact 
with the Coppatias, but also at those points at which it was liable to 
' It is noteworthy that there are none of the characteristic nodular amphias- 
ters present in the parenchyma of the Clionid. As I pointed out in my original 
description of this species (Rec. nd. Mus. XI, p. 20), these spicules often occur in 
great abundance in association with a horny membrane covering projecting parts 
of the sponge, in circumstances that suggest that they are utilized in excavating 
fresl. papillae. It is now evident that the secretion of horny substance is not 
necessarily correlated with their development. 
