PHYSIOLOGY OF THE INVERTEBRATA. 329 



fine nerve-fibres. The anterior corner of the cerebral ganglion 

 is exserted to a narrow point, appliedagainst the posterior angle 

 of the ocellus. The antennular nerves, apparently originat- 

 ing from the posterior part of the cerebral ganglion, may 

 be easily traced as a delicate stem running along the axis of 

 the antennulee and dividing at their extremity into a number 

 of nerve-fibres, which end with numerous ganglionic cells, 

 filling up the dilated terminal part of these organs at the base 

 of the sensory filaments. The nerves of the antennse do not 

 seem to arise from the cerebral ganglion itself, but from the 

 strong commissures enconipassing the oesophagus. The closer 

 structure of these nerves, and the mode by which they 

 innervate the several parts of the antennse. Dr. Sars has not 

 succeeded in tracing out. 



The ventral nervous system, and especially its anterior 

 part, is very difficult to examine. By carefully dissecting 

 the trunk, and spreading it out in a ventral aspect after the 

 intestine had been removed. Dr. Sars has succeeded in partly 

 tracing out the double nerve-cord, which seems to agree in 

 structure precisely with that in other known Phyllapoda, 

 exhibiting the peculiar ladder-like appearance characteristic 

 of those animals. 



In the Cirripedia, " the nervous system consists of a pair 

 of cerebral ganglia situated in front of the oesophagus, and 

 connected by long commissures with the anterior of five pairs 

 of thoracic ganglia, whence nerves are given off to the limbs. 

 In the middle line, the cerebral ganglion gives off two slender 

 nerves, which run parallel with one another in front of the 

 stomach and enlarge into two ganglia, when they are con- 

 tinned to a double mass of pigment, representing the- eyes. 

 From the outer angles of the cerebral ganglion arise the large 

 nerves, which proceed into the peduncle and supply the sac. 

 These appear to correspond with the antennary and frontal 

 nerves of other Crustacea; and Mr. Darwin describes an 

 extensive system of splanchnic nerves."* 



* Huxley's Invertebrata, p. 295. 



