1912.) N. ANNANDALE and S. Kemp: Kumaon Lakes. [41 
continuity with it, the dorsal end gives rise in some zooecia to 
a small semicircular projection or hood even darker than itself but 
somewhat more flexible. At each side of the periphery a project- 
ing valve, which is colourless, softer and still more flexible, is formed 
in continuation of the stiffened wall, and the two valves are joined 
together round the ventral end by a narrow fringe of integument 
similar to that of which they are themselves formed. ‘The term1- 
nal wall of the zooecium may therefore be said to be surrounded for 
the greater part of its extent by a projecting fringe or border the 
surface of which has the roughened appearance characteristic of the 
external ectocyst, although the colour and stiffness of the latter are 
absent. Although I talk of this structure as a projecting Lorder, 
its distal margin is, as a matter of fact, in direct continuity with 
what becomes the proximal end of the tentacle-sheath when the 
polypide is fully extended, just as its proximal margin is in conti- 
nuity with the wall of the zooecium. 
Fig, 2.—Part of zoarium of P. tanganyikae from Cuttack, x 10, with the tip of 
a single zooecium, x 60. 
When the polypide retracts its lophophore, the hood (when 
it is present) is drawn downwards to a slight extent, owing to the 
fact that it is attached distally to the tentacle-sheath, and bends 
over the orifice. For the same reason the lateral valves close 
together tightly, completely covering the orifice. If retraction of 
the lophophore is spasmodic or unusually violent the valves are 
dragged into the zooecium so far that a kind of antechamber is 
formed above them, of course open at the tip. When the lopho- 
phore is extended, the valves are thrust apart and the hood is 
forced into line with the end of the orificial wall. Before the 
tentacles emerge, however, a bulbous transparent mass appears 
between the valves and forces them asunder. It is the still 
partially-invaginated tentacle-sheath. 
It was not until I had had an opportunity of examining at 
leisure with a binocular microscope healthy living colonies of 
