Introductio7i to Animal Morphology. 227 



through the intestinal wall. The fluid is aerated at 

 the tentacles or body surface. 



Each persona has a yellow, oval or lobed ganglion 

 between the mouth and anus, sending two strong 

 branches to the tentacles and two to the oesophagus, 

 round which they make a ring (Fredericella, &c.) 

 Below this may be a sub-oral, pharyngeal ganglion in 

 a few cases [Dumortier). Serialaria and other cteno- 

 stomatous, branched forms have a colonial nerve-system, 

 taking its origin from a ganglion at the base of each 

 branch of the stock, which unites by fine plexiform 

 branches with the nerves of each persona. This ex- 

 plains the consentaneous action noticed in a colony 

 such as Mimosella. 



No special sense-organs exist, except perhaps the ciliated 

 body near the ganglion in Pedicellina ; but many colonies of 

 freshwater forms show by their motions that they are sensitive 

 to light. The muscular lamina is never complete, but con- 

 sists of specialized bundles, which are — ist, two retractors of 

 the lophophore ; 2nd, retractors of the polypide, from the floor 

 of the cell to the oesophagus ; these lie in the axis of the 

 pillar in Pedicellina ; 3rd, two rotators of the lophophore, in 

 the freshwater form ending in each corner of the crescentic 

 disc ; 4th, retractors of the tentacles from the lophophore, 

 placed between each pair of tentacles, sending a branch on 

 each side ; 5th, the levator of the epistome ; 6th, Parieto- 

 vaginalis anterior, many short transverse bands from the 

 invaginated part of the endocyst to the protrusible part ; 

 7th, Parieto-vaginalis posterior, stronger, behind the last, to 

 the permanently retracted part of the endocyst ; 8th, Parietalis, 

 annular body fibres, whose anterior fibres are the sphincter 

 vaginalis. Besides these, there are radiating fibres joining 

 the two valves of the Avicularia, and opercular muscles in 

 Chilostomum. 



The irregularly rounded testes are either seated 



