314 WILLIAM A. HASWKLL. 



has the shape in different regions sometimes of an entire 

 oval, or is bilobed, or more or less deeply cleft, or even com- 

 pletely divided. The gang-lia consist of very slight enlarge- 

 ments of the fibril lated cord, covered on its ventral and 

 latei'al aspects with the nerve-cells ; where a nerve is given 

 off, the group of nerve-cells is produced for a short distance 

 around its base. 



There are five ganglia, one for each segment, in the 

 internal region of the body. The first ganglion is short, but 

 (as regards its group of nerve-cells) expanded transversely. 

 The fibrillated cord is here deeply divided into right and left 

 portions, each continuous with the oesophageal connective of 

 its side. The second ganglion, which is very close to the 

 first, is of much larger size ; it is situated opposite the cirri 

 of the first pair, and gives off a pair of nerves ending in a 

 pair of ganglia at the bases of the cirri. From the nerve- 

 cells of these lateral ganglia nerve-fibres pass along the 

 axis of the cirri to the extremities, where they terminate in 

 connection with the sensory cilia. In transverse section the 

 second ganglion appears very distinctly double, especially in 

 its posterior portion ; in the female it is completely divided 

 into two parts, separated by a definite gap. The connection 

 between the second and third ganglia is of considerable 

 length, and is very distinctly double. The third ganglion 

 gives off a pair of nerves to a second pair of lateral ganglia. 

 In the male the fibrous cord is not distinctly divided, but 

 further back it is divided into two completely separated 

 though closely apposed portions ; in the female it is deeply 

 divided throughout. The connection between this and the 

 fourth ganglion is not cleft, but only obscurely divided in the 

 male ; in the female it is deeply cleft. The fourth ganglion 

 is situated opposite the claspers in the male, and in a corre- 

 sponding position in the female. It gives off a pair of 

 nerves which in the male supply the claspers, while in the 

 female they end in a pair of small lateral ganglia. In the 

 anterior part of this ganglion the cord is not divided ; further 

 back it is bilobed ; yet further back it is undivided and 



