39 



however, IkikUy as diioct as in the Diore primitive 

 Docoglossa [e.fi., Acinaa). From the pleural centres are 

 also given oli' the nerve hands which together form the 

 visceral loop. 



A first examination seemed to show a sU'iider nerve 

 connecting the two pleural centres together, and running 

 just in front of the ])edal commissure. Microscopic 

 investigation, however, shows that this slender cord is a 

 tibrous band connecting the two otocysts and extending 

 beyond them to end in the dorsal surface of the foot. 



T he Labial an d B u c c a I X e i' v o u s 

 S y s t e m. — A fairly thick connective arises from the 

 inner border of each cerebral ganglion, and goes along 

 the floor of the snout, very soon swelling into what may be 

 called a labial ganglion. The commissure between the 

 labial ganglia is thin and markedly curved, with the 

 concavity forwards, the curve being underneath the 

 sub-lingual ])ouch. The labial ganglia give rise to nerves 

 going forwards to the lips, and, at the back, to a few 

 supplying the snout muscles, &c. (see hg. 2-j). From each 

 of these ffang-lia also arises a fine sinuous labio-buccal con- 

 liective, which enters the tissue of the odontophoral 

 cushion. When it reaches the dorsal surface of this (ugan 

 it swells into an elongated buccal ganglion. The two buccal 

 ganglia converge to some extent posteriorly, and are 

 connected with one another by a well-marked commissure 

 entering their posterior extremities. The buccal nervous 

 system is easily seen on removal of the gullet and the 

 radular sac, but the connection Avith the labial centres 

 is difficult to trace. The labio-buccal connective gives 

 off a nerve to the anterior parts of the odontophore. Each 

 buccal ganglion gives rise, at its anterior end, to a nerve 

 supplying the lateral muscles of the odontophore, and 

 several small nerves arise from its inner border. A well- 



