NERVOUS SYSTEM OF PYCNOGONIDS 



469 



than the others mentioned. The first larval stage soon attaches 

 itself to, and enters hydroids. It has three appendages in the 

 first larval stage, one pair is chelate, the last two have long ten- 

 dril-like extensions. At such a period the nervous system is 

 not easily made out from surface views, but it is much hke that 

 of Ammothella. Figure 8 shows three parts, a larger thicker 

 portion which has nerves to the larger first appendages, and 

 on each side back of this a group of cells corresponding to the 

 other appendages. A moult within the hydroid gives rise to 

 a small larval form without the long appendages and it is at 





/ 



.1: .i\ \ 



14 



/ \ 



16 



Fig. 14 Outline of ventral view of larva and ganglia from holow A. erectus, 



third larval stage. X 85. . ., c , i f a 



Fig. 15 Outline of a ventral view of a later stage larva than figure 14 ot A. 



erectus. X 85. , ^ xl *. 



Fig. 16 Outline of a dorsal view of a larva of A. erectus about the same stage 



as figure 14. The brain is shown. X 85. 



Fig 17 Fourth stage larva of A. erectus from below. X 35. 



Fig 18 Central ganglia of a larva of A. erectus with three pairs of walking 

 legs. The drawing is from below. The upper area without nerves in the fagure 

 is the supraesophageal ganglion. X 35. 



