CHAETODERMA ATTENUATA. 57 



be considered to be a subradular system with ganglia and connectives with fibres 

 passing into the above described organ in front of the radula. The labio-buccal 

 connectives pass backward as usual and unite with the well-known ganglia 

 imbedded in the pharyngeal nuisculatiu'e: and these bodies are in turn united 

 by a cord in which two small ganglia are intercalated. A nerve which appar- 

 ently has escaped observation arises from the posterior surface of each of the 

 larger ganglia (Plate 13, fig. 3), and imbedded in the pharyngeal wall may be 

 traced to the forward border of the stomach. 



A short distance in front of the labio-buccal ganglia a clearly defined fibre 

 arises from each of the connectives (Plate 13, fig. 3), and, imbedded in the muscle 

 of the pharynx, courses downward and inward and joins a ganglionic mass that 

 gives slight evidence of being paired (Plate 25, fig. 10). To the outside of the 

 ganglion (or ganglia) a nerve arises from each of these connectives uniting with 

 the labio-buccal connectives, and coursing dorsally attaches to the base of the 

 subradular organ. 



There is absolutely no doubt of the existence of this system, the grayish 

 nerves showing with great distinctness against the yellowish muscle fibres in 

 material killed in vom Rath's fluid. In material fixed in alcohol on the other 

 hand it is sometimes difficult to trace. The ganglionic mass may closely re- 

 semble a salivary gland and the nerves from it counterfeit muscle fibres; never- 

 theless with an oil immersion lens I have been able to demonstrate its presence 

 in all the species of the genus described in the present paper, and in a specimen 

 of C. niliduium kindly sent me by Professor Hubrecht. As is more fully noted 

 on page 172 I believe that the ganglion and its connectives constitute a subradular 

 system the homologue of the one I have described in some of the Neomeniidae. 



Posteriorly the pedal and lateral ganglia unite in the customary fashion, 

 and at the, point of union give rise to two small nerves which become closely 

 applied to the body wall, and after branching are lost to sight among the longi- 

 tudinal somatic muscle fibres. From the suprarectal ganglionic mass (Plate 12, 

 tig. 4), several branches arise some of which appear to have escaped observation, 

 or at all events have not been traced to any considerable extent. Of these the 

 larger pair originate from the ventral side of the ganglion and make their way 

 ventrally to the sides of the rectum, where according to Wiren's figures and 

 description they diminish very rapidly in diameter and form a delicate subrectal 

 commissure. In the present species this is certainly not the case, nor is it true 

 of C. erudita, for arriving at the rectum each follows it posteriorly to the anal 

 opening, and then passes outward almost at a right angle and becomes imbedded 



