404 HAROLD HEATH, 



posteriorly to point corresi)()n(Jiiig closely to the hinder end of the 

 salivary glands. Anteriorly each breaks up into a number of branches 

 that become lost amid the muscle and connective tissue a short 

 distance behind the brain in close j)roximity to the branches from 

 the dorsal commissure. 



The buccal ganglia (b.g) are relatively large structures slightly 

 imbedded in the pharyngeal wall on each side of the radula. From 

 the posterior borders of each the commissure takes its rise and im- 

 bedded in the muscular pharyngeal wall passes behind or dorsal to 

 the radula. In one specimen there appeared to be fibres originating 

 from the commissure and entering the surrounding muscles but in 

 the other two specimens this was apparently not the case. On the 

 other hand two or three nerves are invariably developed from the 

 buccal ganglia and some of their branches may be traced for a con- 

 siderable distance in the pharyngeal wall. 



In a foregoing paragraph attention has been called to two groups 

 of high columnar cells situated immediately in front of the i-adula on 

 each side of the mid-line. Each group is roughly hemispherical in 

 form and in one specimen is partially enveloped in a fold of the sur- 

 rounding tissue (Fig. 5). In another individual it is more exposed. 

 Furthermore this organ is not only subradular in position but in its 

 finer histological details is strikingly like the subradular organ in 

 the Chitons; in fact a description of one answers equally well for the 

 other save that in the Chitons it is ciliated and in the Solenogastres 

 it is not. It has long been known that this organ in the Chitons is 

 a paired structure. The epithelial cells composing it form two closely 

 united masses innervated by the appressed subradular ganglia. In this 

 species of Solenogastre the two halves of the organ, or better the two 

 organs, are dorsally completely covered by the radula and are separated 

 by a distance equal to half of its width. In a contracted condition 

 they are beneath the front end of the radula but in an everted condition 

 they project somewhat beyond it into the cavity of the pharynx. 



Slightly behind and to the outside of each subradular organ the 

 subradular ganglia are located (Figs. 1, 4 s.r.y). They are globular 

 in form, clearly differentiated and measure in diameter approximately 

 one third that of the subradular organ. The commissure uniting the 

 ganglia and the connectives leading to the buccal connectives may be 

 determined without much difficulty in sections but it is a tedious and 

 delicate operation to trace them through the muscles that are largely 

 instrumental in moving the radula. In sections fine fibres may be 



