62 Journal of Entoniolog\ and Zoology 



charactcriMic positions. Also on the dorsal side llicre are (wo peculiar fiber masses in 

 symmcirical positions. 



The pedal ganglion is small and just in front of the visceral. Il is almost a 

 pan of the visceral and closely applied to it. It has two chief nerves on the cephalic 

 side. Its central fibrous mass is slight. 



Explanation of Figures. 



Fig. 4. Chief ganglia of Piddock. The cerebral ganglia are above, the vis- 

 ceral mass with the small pedal ganglion attached below. X9. 



Fig. 5. One cerebral ganglion with part of the connective. X350. 



Fig. 6. One cerebral ganglion, a branch above, the connective to the left, the 

 commissure branch to the right. X70. 



Figs. 7, 8 and 9. Sections through three levels of the visceral ganglion. The 

 dorsal side is up. X70. 



Fig. 10. Section through the pedal ganglion with the two connectives as isolated 

 pieces each side. The dorsal side is up. X70. 



