The nervous system and snbradnlar organ in two genera of Solenogastres. 403 



probably the hypodermal sense organs of the under side of the 

 animal. 



Each palliai cord after leaving the brain also enters the anterior 

 pedal gland and soon takes up a permanent position along the sides 

 of the body. From it nerves originate that coursing dorsally or ven- 

 trally supply those regions not directly connected with the pedal 

 system. Pallio-pedal connectives appear to be about as numerous as 

 pedal commissures and anteriorly they probably commence at the same 

 level. In the study of sections they are to be ditïerentiated from or- 

 dinary nerves only in exceptional cases. On the other hand dis- 

 sections show with the greatest distinctness that at points roughly 

 corresponding to the intervals between the gut pouches connectives 

 are present. At times these are of extreme tenuity but in this species 

 of Proueomenia their attachment to the body wall or to the gut is 

 slight and with careful manipulation their relations may be demon- 

 strated beyond question. Unlike the pedal commissures they frequently 

 develop branch<îs that may be traced to the surface of the gut or to 

 the body wall. 



Before considering the buccal system a brief comparison will be 

 made with the brain and its chief nerves in Rhopalomenia. These 

 are shown in slightly diagrammatic fashion in Fig. 2. It will be seen 

 that neglecting minor ditierences the nerves arising from the front 

 end of the brain are similar in origin to those in Proneomenia and 

 dissections show them to have essentially the same distribution. The 

 pedal, palliai and buccal connectives are likewise similarly related in 

 both forms. Owing to the relatively large amount of muscle and con- 

 nective tissue and the small size of the nerve fibres it is difficult to 

 trace these to their destination by means of dissections. With the 

 pedal commissure also it has been possible to follow merely the first 

 and a few succeeding ones. Somewhat less difficult is the tracing of 

 the pallio-pedal connectives but these do not appear with the diagram- 

 matic clearness of those in Proneomenia. 



The buccal connectives pass almost horizontally backward and are 

 free in the visceral cavity or only slightly attached to the visceral 

 wall. At a point about midway between the brain and the buccal 

 gangha a dorsal commissure (Figs. 1,4) is developed that rests upon 

 the dorsal wall of the pharynx. On each side of the mid-line it gives 

 rise to a nerve that extends forward and after branching repeatedly 

 becomes lost in the tissues of the pharynx. Furthermore there is a 

 pair of nerves on the sides of the dorsal aorta which may be traced 



