12 



INVERTEBRATA. 



FIG. V. 



THE SLUG. 



(LIMAX ATER.) 



THE slug was opened on the dorsal surface ; the brain is seen placed above or on 

 the dorsal portion of the oesophagus, and giving filaments to the feelers, and the parts 

 about the mouth ; a ganglion is seen larger than the brain, placed beneath or next 

 the ventral surface of the oesophagus, and connected by a narrow band with the brain. 

 The nerves are seen proceeding from the ganglion principally to the fleshy foot and 

 integuments, and giving some small branches to the heart and digestive organs. 



FIG. VI. 



THE WHELK. 



(BUCCINUM UNDATUM.) 



AFTER dividing the surface from the edge of the broad end of the foot towards 

 the parts contained in the apex of the shell, a pink substance resembling a ganglion 

 is seen on the proboscis ; it is connected by filaments on each side to the contiguous 

 parts and the nervous ring. 



