1915. | N. ANNANDALE: Parasitic Sponges. 477 
be attacked by a flank movement. A number of its macroscleres 
project through the horny covering into the body of the invader. 
When Cliona ensifera or C. viridis is attacked by a Chondrilla 
a similar horny coating is produced and a mass of macroscleres is 
formed lying parallel to the tranverse axis of the part with which 
the attacking sponge is in contact. This also occurs when C. vim- 
dis is attacked by Rhabderemia prolifera, but the horny coating is 
very thin. 
It therefore appears that the mode of defence adopted by the 
Clionid is not always precisely the same, even in cases in which it 
can be adduced with practical certainty from observations made 
on preserved material. There are other methods of defence that 
can only be surmised from general considerations. One of these 
is possibly the production of diaphragms in the galleries of the 
Clionidae. In C. mucronata these structures are remarkably well 
developed and are protected by highly specialized spicules. It is 
perhaps more than a coincidence that I have not found any ex- 
amples of this species that were overwhelmed or even attacked 
by other sponges. 
I have pointed out elsewhere! that the gemmules of the 
Clionidae are possibly useful in permitting regeneration after the 
parent sponge has been suffocated by the growth of encrusting 
forms over its papillae. The production of gemmules in C. annuli- 
fera and Thoosa investigatoris at a depth of over 700 fathoms is 
particularly interesting, because at depths of such magnitude it is 
probable that conditions remain identical, so far as temperature, 
currents, etc., are concerned, throughout the year. It is only in a 
very few species of Clionidae that resting bodies of the kind have 
been discovered and I am convinced that they are not asa rule 
produced in Indian species other than the two just mentioned and 
the shallow-water form C. vastifica. In both the deep-sea species 
the gemmules are of a highly specialized character. In C. annuli- 
fera they are provided with spicules of a type that does not occur 
in the vegetative part of the sponge. These spicules are micro- 
scleres of an unusually large size; they cover one surface of the 
somewhat lens-shaped gemmule in a dense horizontal layer, form- 
ing a regular shield, but are entirely absent from the other surface. 
The surface that they protect is the one in contact with the parent 
sponge, that is to say the one with which an invading sponge would 
come in contact if it made its way along the galleries already ex- 
cavated. The naked surface is in contact with the walls of the 
excavations, which protect it in the natural position. 
The gemmule of T. investigatoris is very different from that of 
C. annulifera. It has neither a horny covering nor spicules of any 
kind, but is hidden away in a special chamber excavated in some 
unknown manner for its reception, and is only connected with the 
parent sponge by an extremely fine strand of living matter en- 
closed in a narrow canal. 
= | Mem. Ind. Mus. V, p. 35 (1915). 
