NERVOUS SYSTEM OF THE POLYZOA. 305 



examination should not be concealed by the cells^ Avhich, in 

 most cases, are closely contiguous, the latter must be so disposed 

 as to lie on the side. But in this case the part to be examined 

 is brought, in the first place, close to the border of the cylin- 

 drical branch, and secondly, into almost the same plane with the 

 cutaneous pigment ; and, consequently, for both these reasons, 

 it is often nearly opaque. The stomach, moreover, of the 

 retracted polypide is usually in the way of a distinct view. 

 Nevertheless, in almost every branch, one or another polypide 

 or, more readily still, budding cells will be found, in which 

 the nervous connection in question will be unmistakably 

 presented. At the point of junction between the cell and 

 branch, and projecting half into the one and half into the 

 other, a spherical ganglion, from O'O-l to 0*05 mm. in 

 diameter (smaller in young buds), will be seen lying. This 

 ganglion is connected, on one side, with the nerves of the 

 plexus, whilst from the other I have several times, in the 

 full-grown polypide, fancied that I could see a nerve pro- 

 ceeding to the intestine ; and this is certainly the case in 

 the buds. A connexion between this basal ganglion and the 

 oesophageal ganglion of the polypide may be supposed to 

 exist, but this I have not been able to trace. 



The radical fibres, also, whether they arise at the extremity 

 of a branch, or in the line of a series of cells, or elsewhere, 

 also have each its basal ganglion and longitudinal nerve-trunk. 

 At their first appearance the polypide-cells and the branches 

 of the polyzoary are not distinguishable from each other in 

 any essential particular beyond their place of origin, whilst 

 as regards the radical fibres even this distinction does not 

 obtain. In these three structures may be perceived a happy 

 exemplification of Leuckart's doctrine of polymorphism. 



It may be expected that a similar common nervous system 

 will be found in other Polyzoa, in which the cells are seated 

 on a distinct rachis ; '" whilst in those forms in which one 

 cell springs from another [Cheilostomata and Cyclcstomata] 

 ganglia may be supposed to exist, at any rate, in the base 

 of each cell, and connected with each other by nerve-fila- 

 ments. 



[The author adds tliat, since the above Avas written, he had 

 found the basal ganglia of the branches and the nerve-trunk 

 in various Ctenostomata, Busk ; but that up to the present 

 time he had failed to discover any indubitable trace of a 

 common nervous system in the other Polyzoa.] 



"* [A.11 the Ctenostomata.] 



