CEPHALODISCUS. 



105 



consist of a flexible, brownish semitransparent material. The 

 tubes are composed of superposed lamellae and are probably 

 secreted by the proboscis of the animal (see below). The organ- 

 isms are not attached to each other or to the wall of the tube in 

 anyway, but appear to have the power of moving freely about 

 inside it. Scattered about here and there on the tubes are large 

 rounded apertures, near which the individuals are often found, 

 and through which they can protrude their tentacular tufts. 

 The tubes are covered with tapering spinous processes of their 

 walls. The cavity of the tube may be continuous or it may be 

 divided up into cham- 

 bers, one for each in- 

 dividual or zooid. 

 With regard to the size 

 of a colony it may be 

 mentioned that in Ceph- 

 alodiscus dodecalophus 

 the network of tubes 

 covered an area of 9 

 inches by 6 inches. 

 The stems have a dia- 

 meter of from 4 to 10 

 mm., and the whole 

 colony appears to have 

 been attached to mar- 

 ine objects such as 

 stones, sponges, etc., 

 by vertical stems which 

 descend from the 

 underside of the net- 

 work to the substratum. The natural position of the colonies 

 would thus appear to be horizontal. The full-grown individuals 

 of C. dodecalophus measure about 2 mm. in their longest diameter. 



Cephalodiscus may be described as an animal in which the or- 

 anal axis of the body is very short and the ventral surface behind 

 the mouth is produced into a large hump in which the alimentary 

 canal is continued (Figs. 77, 78). This ventral hump terminates 

 at its ventral and anterior end in a pedicle on which buds are 

 continually being formed. 



The mouth is ventral and anterior and is overhung by a large 



FIG. 77. Cephalodiscus dodecalophus, anterior view (after 

 Mclntosh). 1 tentacles ; 2 proboscis (buccal shield) ; 

 3 pigment band on proboscis ; 4 buds ; 5 pedicle ; 6 

 trunk. 



