41 



(<■) Smaller nerves witk (loubthil disti ihutioii. 



Ei(mi ihe viseenil ganglion the loop goes on towards 

 the animal's riglit side, attaining its extreme position in 

 this direction near where it emerges in front from the 

 visceral mass, thence it goes across beneath th(> other 

 part of the loop and above the pedal cords to the left 

 plenral ganglion. At the extreme right point a few 

 ganglion cells can be found, and from this point arises a 

 tliin and short nerve going to tlu^ right os])hradiuni, 

 beneath which there is a small osphradial ganglion. This 

 extreme point Avould be the proper j)lace for tlie usual 

 sub-intestinal ganglion, which, therefore, mav be 

 represented by the few ganglion cells found there. It is 

 possible that the vanished ganglion is now included in 

 the left pleural ganglion, which is much elongated and 

 partly divided into two. The " sub-intestinal '" part 

 of the visceral loop, that is the part next the left ])lcural 

 ganglion, gives off a ccmple of slender nerves, one near 

 the pleural ganglion and one further along (hg. 2o). 



It is characteristic of the ])oooglossa that the visceral 

 loop lies entirely to the right of the fore gut, instead of 

 over it and near the right side, as in many other Giastro- 

 pods. This is in relation to the extra torsion of the fore 

 gut which has taken place in the group. 



Sense Organs (tigs. 25, '-20, 27, 28). — A sub-epidermal 

 plexus of primitive type, with couuected sensory cells, 

 still remains in some parts of the body, notably in the 

 sides of the foot of the young animal, but we also have 

 concentrations to form si)ccialised sense organs. These 

 are the cephalic tentacles, the eyes, the otocysts, the 

 osphradia, and the pallial tentacles. 



The Cephalic TctitacJe.^ are a pair of specialised sensory 

 out-growths, situated at tho sides of the snout (figs. 4 and 5). 

 They are extremely extensible, and their surface appears 



