TQI2.] N. ANNANDALE: Sponges of the Malabar Zone. 389 
The fixed and free gemmules are apparently analogous in 
function to the fixed and free statoblasts of Plumatella. ‘The 
fixed reproductive bodies of both sponge and polyzoon serve to 
ensure renewed growth of the organism in a situation that has 
already, in certain conditions, proved favourable for its proper 
development. Their production is either correlated with a change 
in conditions or perhaps in some few cases precedes any such 
change and is due rather to a form of senescence. Conditions 
suitable for renewed activity on the part of the organism are 
similarly either correlated with or antecedent to renewed vegeta- 
tive growth on the part of the resting bodies. The free gemmules, 
on the other hand, are carried away by floods and thus aid in the 
dispersal of the species. So far as the facts as yet ascertained 
justify a statement as to conditions that bring about or precede 
the production of the two kinds of gemmules in Corvospongilla, 
it would seem that the fixed gemmules are formed as soon as the 
sponge is in full vigour or just past its prime, and that the free 
gemmules are formed at a later season. Sponges of the genus 
frequently occur on the beds of rocky streams that rise with great 
violence in the ‘‘rains”’ but sink to a series of more or less dis- 
connective pools in the cool season. They are often left high and 
dry at the latter time of year. Their compact skeletons remain 
firmly adherent to the rock until the floods come again. Then, 
in all probability, the free gemmules are washed away to places 
down stream, while the fixed gemmules cling fast and in due 
course produce a new sponge on the old basis. 
Key to the Indian Forms of Corvospongilla. 
I. Majority of the megascleres sharply 
pointed. 
1. Delicate species with only free 
gemmules a .. C. caunters. 
2. Much stouter species with fixe 
(and sometimes also _ free) 
megascleres, 
(a) External surface rough but 
not spiny .. C. ultima (typical). 
(b) External surface distinctly 
spiny Be .. C, ultima var. spinosa. 
II. Majority of the megascleres distinct- 
ly amphistrongylous. 
I. Sponge hard but brittle, radial 
spicule-fibres produced  verti- 
cally upwards to form spines 
on external surface. 
(a) Oscula elevated on cylindri- 
cal, turret-like eminences.. C. burmanica. 
