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WILLIAM A. HILTON 



such a period that new ganghonic material seems to be developed. 

 Figures 9, 11 and 14 are drawn from such early stages. At 

 a later moult more gangha are evident, as in figures 10, 15, and 

 16. The ventral ganglia at first are mere groups of cells, as 

 is shown in the frontal section from which figure 10 was taken. 

 As may be seen from the figures 10 and 15, ganglia are devel- 

 oped in each segment, a pair for each appendage and several 

 for the cephalic region and a connnon mass of cells for the ab- 



Fig. 19 A longitudinal section through the central ganglia of Lecythorhynchus 

 marginatus, Cole. Two small abdominal ganglia show at the end of the last 

 thoracic ganglion. X 35. 



Fig. 20 A longitudinal section through the supraesophageal ganglion of L. 

 marginatus. The dorsal side is up, the cephalic side to the right. X 210. 



dominal. In a stage just before this there are two pairs of 

 ganglia on the dorsal side of the larva; these are shown in fig- 

 ure 16. They represent the brain. 



At about the third moult, as shown in figures 12 and 17, the 

 ganglia have developed central fibers, but still show their paired 

 nature. There seems to be some indication of more ganglia 

 than there are appendages, some of the caudal elements may not 

 be evident in later stages, and the first ventral ganglion seems 

 composed of two small pairs of elements. In the proboscis 



