92 BALANIDJE. 



nerves, though these latter are always described as uniting 

 into a single medial branch. The plexus (d') is the cervical 

 ganglion of M. Martin St. Ange,* who has likewise indi- 

 cated the course of my splanchnic and supra-splanchnic 

 nerves ; but the plexus, when viewed as a transparent 

 object, hardly appears to me to be ganglionic in its nature. 

 In my former volume on the Lepadidge, I quite misunder- 

 stood the course of these splanchnic nerves. 



From the commissure between the two supra-cesophageal 

 ganglions, a straight chord (PL 27, fig. l,y) arises, which 

 terminates in a small ganglion (c), barely exhibiting traces of 

 being formed of two laterally confluent ganglions. This is the 

 ophthalmic ganglion. The chord connecting it with the two 

 supra-cesophageal ganglions is accompanied by a small nerve 

 (h) which runs on to the muscles round the adductor scutorum 

 muscle ; the chord is encased by much fibrous tissue, and its 

 dissection is thereby rendered difficult. From the ophthalmic 

 ganglion, on each side, a nerve (i) goes forth and crosses 

 the antennular nerve ; these, if I could have traced them, 

 would have been found to run, as may be safely inferred 

 from what is known in Balanus tintinnabulum, to a pair 

 (d, d) of eyes. 



In Balanus tintinnabulum, the structure of the great infra- 

 oesophageal ganglion (PL 27, fig. 2, a) is essentially the same 

 as described under Coronula. The great pair of splanchnic 

 nerves springing from its under side, are here actually twice 

 as large as the circa- oesophageal chord. The plexus {d') 

 formed by the splanchnic nerve id), on each side, with the 

 supra-splanchnic nerve (e), which arises close posteriorly to 

 the supra-cesophageal ganglion, is here much less compli- 

 cated, but is perfectly distinct ; and there was no appear- 

 ance of the cervical ganglion of M. Martin St. Ange. The 

 chord (y) running from between the two supra-cesophageal 

 ganglions to the ophthalmic ganglion, is nearly as large as 

 the double antennular nerve (/) on each side of it. The 

 ophthalmic chord (which is accompanied in its whole course 

 by a small branch running to the adductor scutorum muscle) 

 terminates in a small ophthalmic ganglion (c), which seems 



* t 



Memoire sur ^Organisation des Cirripedes,' p. 19. 



