ZOOLOGY 
flagellata, with no collar round the base of the flagellum; and 
Fic. 18.—A branch of Codo- 
siya cymosd, Sav. Kent. 
1. The stalk. 
2. Protoplasmic cell body, 
showing nucleus and 
granular protoplasm. 
3. Collar. 
4, Single flagellum. 
J 
Most Flagellata live in fresh water ; some are marine, and 
some parasitic, living in the alimentary canal or blood of 
the Choanoflagellata, in 
which the protoplasm is 
produced into a collar which 
surrounds the anterior end, 
from the middle of this the 
single large flagellum takes 
its origin. Codosiga (Fig. 18) 
isa colonial form of this kind, 
composed of long branching 
stalks, the end of each branch 
bearing an ___ individual. 
These collared flagellates 
have a striking resemblance 
to the collar cells lining 
the flagellate chambers in a 
sponge; and a genus, Pro- 
terospongia (Fig. 19), dis- 
covered by Saville Kent, in 
which the individuals of 
the colony are sunk in a 
jelly, lends some support 
to the view that Sponges 
may have originated from 
colonies of Choanoflagel- 
lata. In this genus the 
individuals near the sur- 
face are of the typical 
form; but certain wander- 
ing amoeboid cells have 
sunk into the central jelly, 
and some of these have 
become spherical, and then 
divided up into micro- 
gonidia, in a manner recall- 
ing the formation of sper- 
matozoa in a Sponge. 
