248 



A. IZUKA. 



nerves are connected together by a ring-nerve. That pair of proboscidial 

 nerves that arise from the anterior cirrus ganglia terminates at the ring-nerve, 

 while the rest of them are continued beyond it So that, in the anterior 

 parts of the protruded proboscis there are again four pairs of longitudi- 

 nal nerves in the outer wall : viz. two dorsal pairs, one lateral pair and one 

 ventral pair. The two dorsal nerves of each side are continuations of the 

 branches of the I. cerebral nerve ; the lateral nerve is that of the VII. 

 cerebral nerve and the ventral nerve, that of the nerve coming from the 

 ventral part of the (esophageal connectives. All the nerves are again 

 joined together by a ring-nerve running in the free edge where the outer 

 wall of the protruded proboscis turns back to form the inner This 

 ring-nerve shows on the dorsal side of the proboscidial orifice a pair of 

 moderately large and lobed ganglionic swellings, the proboscidial ganglia 

 (j>r. Small ganglionic swellings are also observed on the ventral side 

 at the two points where the ventral nerves from the oesophageal connectives 

 join the nerve-ring. 



The terminal nerve-ring are seen to send forth two pairs of nerves 

 into the inner wall of the protruded proboscis. One pair arises from the 

 proboscidial ganglion ; the other pair, a short distance medianly from the 

 point of junction of the ventral nerve that comes from the oesophageal 

 connectives. In the inner proboscidial wall, the nerves divide and 

 anastomose, thus bringing about a plexus. 



3 Of Ihe Segmental Organ. 



The segmental organ can be easily dissected out. It appears as a 

 small yellowish-green mass of a convoluted tube at the base of each 

 parapodium From that mass, the nephridial body, there proceeds 

 anteriorly a slender elongate canal which pursues a somewhat arched 

 course and which reaches for a short distance into the next anteriorly follow- 

 ing segment and there terminates with a small funnel, the nephrostome. 

 The nephridiopore or the external opening is situated ventral to the 

 nephridial body and therefore can not be observed from above. Thus, the 



