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ARTHUR DENDY. 
(d) The Flagellated Chambers. 
These are more or less spherical sacs (figs. 6 , 7, 10) about 
004 mm. iu diameter, with two wide apertures of about equal 
size placed at opposite poles, whereby they communicate on 
the one hand with an ultimate inhalant lacuna and on the 
other with an ultimate exhalant lacuna. In the same way 
that several chambers open out of one and the same ultimate 
inhalant lacuna, so also several may lead into one and the 
same ultimate exhalant lacuna. Both the inhalant and 
exhalant apertures of the chambers are usually drawn out into 
short and relatively wide cameral canaliculi (fig. 10, i. c. c., 
e. c. c.), but I do not think too much importance must be 
attached to this fact. 
(e) The Exhalant Canal System. 
The ultimate exhalant lacunae 1 (fig. 6, e. L), into which the 
flagellated chambers open usually through the medium of 
distinct canaliculi, collect together and finally discharge their 
contents into branches of the oscular tubes. Each oscular tube 
is a perfectly definite tubular canal about 6 mm. wide, with 
distinct walls of its own, and leads vertically upwards to a wide 
osculum situated on the upper margin of the Sponge. The 
oscular tube itself may readily be dissected out from the 
surrounding choanosome, from which its walls are very easily 
separable. Fig. 5 represents a dissection of the oscular tube 
( o . t.) showing its relations to the osculum (o.) and the openings 
into it of a number of larger and smaller branches. 
The osculaj are wide, circular openings, about 6 mm. in 
diameter, placed iu a row along the upper margin of the Sponge ; 
their position is indicated in fig. 1 by the letters o. o. o., and in 
the same figure a portion of an oscular tube (o. t.) is seen on 
the cut surface. 
In connection with the exhalant canal system I may here 
mention certain spherical cavities (fig. 5, e. c .) lying in the 
1 It is impossible to distinguish sharply between a canal and a lacuna; 
either term might be applied in this case. 
