296 



PROCEEDINGS OP THE NATIONAL MUSEUM. 



VOL. 39. 



front end of the stomach, are given off the large nerves which supply 

 the second antennae. The ganglion is much swollen at the bases of 

 these nerves and plentifully supplied with imclei. From the pos- 

 terior ventral corner of the ganglion close to the esophagus a short 

 and rather swollen azygos nerve extends downward and backward to 

 the labrum. This posterior portion of the ganglion is perforated, as 

 in Cyclo'ps, by muscles connected with the mouth-parts. 



The circumesopJiageal cord. — This is made up of two lateral por- 

 tions, connecting anteriorly and posteriorly with the ends of the 

 ganglia. It is approximately parallel with the body axis and con- 



«vm 



Fig. 16.— Transverse section through the carapace of Ergasilus centrarchidaeum behind 

 the mouth, dvm, dorso-ventral muscles; i, stomach; im, longitudinal muscles; n, ventral 



NERVE cord; 0, UNDEVELOPED EGG CELLS OF OVARY; up, UTERINE PROCESSES. 



nects the dorsal portions of the ganglia only for about two-thirds 

 of their depth. Each lateral portion is nucleated on its outer sur- 

 face, leaving the inner surface next to the gullet and the dorsal sur- 

 face next to the stomach made up of fibers only. It thus possesses 

 the same elements as the ganglia and has been given the name of 

 cord, as suggested by Hartog. Since it has been moved so far back 

 by the migration of the mouth-parts, it could not be expected to 

 give immediate origin to the nerves that supply the second antennae. 

 Whether any of the fibers of those nerves can be traced backward 

 along the ganglion to the commissure can not be determined with 



