532 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



commissure and is sometimes bound up with it for a 

 short distance. It is quite slender — the seven nerves 

 increase in size in proportion as we go backwards — and 

 passes directly forward to the mandible. 



The Second and Third nerves pass directly to the 

 maxillae, and the Fourth, Fifth and Sixth to the 

 maxillipedes. 



The Seventh nerve, which is very broad, comes off 

 at the widest part of the anterior lobe and passes slightly 

 forwards to the chela. With this and the succeeding 

 thoracic nerves two small branches arise which pass 

 upwards and innervate the neighbouring tissues. 



The central lobe of the thoracic ganglion-mass is the 

 product of the fusion of but a single pair of ganglia, 

 whose nerves supply the second pereiopod. The 

 remainder of the thoracic limbs are innervated by 

 branches arising from the posterior lobe. They all pass 

 backwards and then turn sharply outwards, as they 

 reach the segment for which they are bound. The 

 thoracic nerve mass shades into the abdominal com- 

 missures, which — at first bound together — separate 

 themselves as they enter the abdomen. 



The Abdominal Nerve Chain (fig. 38) is of the 

 familiar ladder type. There are five paired ganglia. 

 Each pair, however, is almost indistinguishably fused, 

 and they are connected by paired commissures. The five 

 paired ganglia are situated m segments two to six, that 

 belonging to the first segment being fused with the 

 thoracic ganglion mass. From each ganglion branches 

 are given off in a somewhat irregular fashion to the 

 muscles, integument, and to the pleopods, and at least 

 one pair of nerves arises from the inter-ganglionic 

 commissures. 



