INVERTEBRATA. 



PLATE II. 



VENTRAL ASPECT OF THE GRAB. 



(CANCER PAGUEUS.) 



THE nervous ring is seen sending branches forward to tlie parts about the mouth, 

 and to be joined by those passing on each side of the oesophagus from the brain ; 

 other branches are seen passing to the muscles of the thorax, to the legs, and the 

 muscles of the tail. The tail is formed of many pieces, somewhat resembling the 

 backs of the rings of the lobster, and in each of them slips of muscle are inserted 

 for drawing it towards the thorax ; the nerve divides into many branches, which 

 terminate in the muscles, but there is not any appearance of ganglia, as in the tail 

 of the lobster, scorpion, &c. 



