40 WALTER K. FISHER, 



a number of branches, which distribute themselves radially and proceed 

 to the tip of the tentacle. Next is the fine optic nerve, which runs 

 parallel and close to the tentacle nerve, straight to the eye, which is 

 situated beneath the integument near the base of the tentacle. The 

 third set arises just back of the optic nerve and consists of a variable 

 number of minute fibres which pass outward to the outer side of the 

 base of each tentacle. 



From the hinder end of each cerebral ganglion the cerebro-pleural 

 and cerebro-pedal commissures pass backward and slightly inward. 

 The former, which is considerably the larger of the two, rises outer- 

 most. Between them and closely appressed to the cerebro-pleural 

 connective the otocyst nerve is seen to originate. This passes back- 

 ward still close to the connective, to the otocyst (ot) which is situated 

 on the ventral surface of each pleural ganglion. As the two com- 

 missures proceed backward they diverge more and more, the pedal 

 bending inward to join the pedal ganglionic mass. From the cerebro- 

 pedal connective of each side there are given ofl* two, sometimes three, 

 nerves to the ventral and lateral walls of the head Q:»'). These branch 

 and some of the twigs anastomose. One or two fine nerves are also 

 given otf from the cerebro-pleural connective. It would appear that 

 the septa separating, from the main buccal sinus, the chambers in 

 which lie the connectives, serve in a measure to protect the com- 

 missures during the vigorous movements of the buccal mass. Several 

 fine nerves are given off to these septa from the cerebro-pedal connective 

 (see Fig. 3). 



The labial ganglia and subradular ganglia (Figs. 37 

 and 38). The two labial ganglia are found imbedded in the pro- 

 tractors of the buccal mass, each one beneath and a little to the side 

 of the subradular pocket. The cerebro-labial commissure departs 

 from the inner and lower side of each cerebral ganglion which is pro- 

 duced or extended toward the labial ganglion of that side. Ganglion 

 cells extend wholly across the connective, though scarce in the middle 

 portion of the commissure. This is also true of the rather more 

 sleuder commissure uniting the two labial ganglia. From the anterior 

 face of each labial ganglion three strong nerves (Ppn) are given off 

 to the palps (Pp). These branch freely and anastomose in such a 

 manner as to form an astonishingly complicated network of nerves, 

 passing upward to the uppermost parts of each palp, and also down- 

 ward to the lower border. A small cross nerve connects the inner- 

 most palp nerves of each side. From the anterior and lower side of 



