440 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The Brain. 



The Brain (cerebral ganglia, e.g.) is situated above 

 the anterior end of the epi stoma. It is roughly 

 rectangular when viewed from above, and is formed of a 

 complex mass of nerve cells and fibres. The anterior half 

 of the brain is connected with the nerve fibres supplying 

 the eye and optic peduncle. From the posterior half 

 arise the nerves innervating the anteimules, antennae, the 

 sense organs of the antennules, and also the nerves 

 supplying the integument. The nerve fibres from the 

 different parts become aggregated in the brain in definite 

 masses or neuro piles (" Punktsubstanz," Leydig). 

 Between the neuropiles there are numerous nerve cells 

 more or less closely packed. The main neuropiles are as 

 follows : — 



Connected with the optic fibres. The ant ero- sup trior, 

 median and posterior optic neuropiles, all situated in the 

 anterior half of the brain. Also the inferior optic 

 neuropile extending below the others. 



Connected with the oculomotor fibres. The paired 

 lateral oculomotor neuropiles situated on the outer side of 

 the optic neuropiles, and also a median oculomotor 

 neuropile lying in the middle line behind the optic 

 neuropiles. 



Connected with the first antenna (antennule). The 

 median neuropile of the first antenna situated in the middle 

 line below the median oculomotor neuropile. The lateral 

 neuropiles of the first antenna situated ventrally at each 

 side, behind the inferior optic neuropiles. 



Connected with the second antenna. There are three 

 neuropiles situated at each side of the posterior region of 

 the brain, viz., the median, posterior and lateral neuro- 

 spiles of the second antenna. 



Connected with the tegumentary nerves. The 



