The anatomy of Lottia gigantea Gray. 41 



each ganglion there also arise two nerves {il, iV) which innervate the 

 lower lips (or posterior, if the head is held in a natural position). 

 The outermost of these nerves seems to anastomose in several places 

 with branches of the labial nerves (wZ'), from the cerebral ganglia. 

 Nerves from the labial ganglia may therefore be said to innervate 

 primarily the palps, and lower lip. From the outer end of each 

 labial ganglion arises the stomatogastric or buccal commissure (StgC). 

 This commissure passes upward around the buccal mass to the stomato- 

 gastric, or buccal, ganglion of its respective side. In its lower portion 

 the commissure is rather flat and ribbon-like, but above becomes con- 

 stricted. A description of the stomatogastric ganglia will be given 

 later. From the lower part of each stomatogastric commissure a fine 

 nerve (hn'") passes downward and backward through the protractor 

 muscles and was lost near the origin of these muscles on the posterior 

 processes of the buccal cartilages. 



BÉLA Haller has rightly contended that subradular ganglia 

 are present in the Docoglossa, but the statement has been denied by 

 various other observers. 



I n Lottia gigantea I have found what I believe to be the 

 subradular ganglia. They are small, and are connected 

 by very definite nerves with the labial ganglia. They 

 are most certainly not connected, as Haller believes, 

 with the pedal ganglia. At the base of the stomatogastric com- 

 missure of each side a slender nerve {Suh. R. C) is seen to depart 

 into the protractor muscle, having a course backward and upward. 

 When about opposite the hinder end of the subradular pouch, this 

 nerve divides into two branches, one passing backward, the other in- 

 ward and forward. This inner branch goes directly to the subradular 

 ganglion of its side. The subradular ganglia {Siib.R. G) are situated 

 on the under surface of the lower wall of the subradular pouch near 

 its hinder end (see also Fig. 4), and sometimes right at the end. 

 Each ganglion lies obliquely, from a direct transverse line, pointing 

 forward. In one or two specimens there seemed to be a very slender 

 commissure uniting the two. To find them it is only necessary to 

 remove the ventral wall of the buccal sinus, working from below, then 

 to remove the protractors and to part the muscles lying above these. 

 The ventral wall of the subradular pouch is then seen, and near the 

 hinder end the two small ganglia. 



Running forward along the ventral wall of the subradular pouch 

 is a very delicate nerve from the inner end of each subradular ganglion. 



