36 Journal of Comparative Neurology. 



bral ganglia. The optic ganglion occupies the dorso-cephalic 

 portion of the brain. It is a median unpaired structure, but its 

 histology seems to indicate that the ganglion has been formed 

 by the fusion of three ganglia. From the apex of the optic 

 ganglion, which is also the apex of the brain, a single median 

 nerve [fig. lo] arises. This is the optic nerve. After passing 

 dorsad a short distance this nerve separates into three branches 

 — one branch for each division of the tripartite median eye [fig. 2] 

 The antennulary ganglia occupy the lateral portions of the 

 brain. From each of these ganglia a nerve arises [fig. 10] 

 which passes latero-cephalad to the antennule of the same side. 

 Near the meson, but ventrad of the optic ganglion, th^re is a 

 pair of ganglia. These I have considered the cerebral ganglia. 

 There is a commissural connection between the two halves of 

 the supra-oesophageal ganglia ; but nothing has been discovered 

 that would lead one to suppose that the nerves decussate within 

 the brain. 



The brain is connected with the ventral chain by two cir- 

 cumoesophageal commissures. These are not true commissures, 

 for about midway between the brain and the ventral chain each 

 commissure contains a ganglion. This is the antennary gang- 

 lion. The antennary nerve [Fig. 3, 8] of each side leaves the 

 corresponding circum-oesophageal commissure immediately 

 behind the brain. A few of the fibres of this nerve arise in the 

 brain, the remainder arise in the antennary ganglion. 



As far as I have been able to ascertain what is known 

 about the ventral chain of the Ostracoda may be summarized in 

 the following words of Professor Lang^ : ' ' The ventral cord of 

 Cythere which follows the brain and oesophageal commissures is 

 said to consist of an infra-oesophageal ganglion and of four sub- 

 sequent ventral ganglia. The infra-oesophageal ganglion is said 

 to show its composition out of two ganglia and to innervate the 

 jaws, while the three subsequent ganglia give off nerves to the 

 limbs, and the last ganglion nerves to the most posterior divi- 

 sions of the body and the genital apparatus. 



^Text book of Comparative Anatomy. Trans, by H. Bernard. 1S91, Vol. i, 

 p. 344. 



