INVERTEBRATA. 



PLATE IV. 



VENTKAL ASPECT OF THE LOBSTEK. 



(ASTACUS MAKINUS.) 



THE greatest portion of the shell has been removed from the preparation from 

 which this plate is taken. The nervous cord is seen about the first ganglion after 

 the junction of the nerves passing on each side of the oesophagus from the brain. 

 Branches are seen passing towards the mouth, and to the contiguous parts throughout 

 the course of the cord ; the nerves to be given to the legs are seen issuing from the 

 ventral surface of the cord. 



The posterior or dorsal layers of the nervous cord do not appear to send distinct 

 fibrils to join the nerves issuing from the anterior or ventral ; and the anterior do not 

 send off branches forming distinct and separate ganglia, in the same manner as the 

 posterior origins in most of the vertebrate animals ; but the gangliform enlargements 

 are concentrated in the cord. 



