Notes on the Central Nervous System of 

 a Free-Living Marine Nematode 



WILLIAM A. HILTON 



The species studied was the one which Is most abundant at Laguna Beach among 

 Algi and in sand at low tide. It corresponds closely to Enoplus brevis Duj. 



The nervous system has several features not described in related forms. There is 

 a concentration of the central nervous system. There is a single large ganglion or 

 brain in the snout above the mouth, from this two connectives pass ventrally to join 

 the broad ventral nerve band in the mid-ventral line, while the only other longitudinal 

 nerve noted was the very small mid-dorsal. Lateral nerves were not found. 



The head or snout ganglion is provided with three eye spots, and unpaired dorso- 

 median and a pair of latero-ventral ones. The sensitive region is so placed as to 

 receive stimuli from above by the median eye and from below by the lateral eyes. 

 The eyes are little more than concave pigment spots imbedded in the mass of the 

 ganglion. .X number of fibers pass from the ganglion forward to supply the thick 

 sensory epithelium of the tip of the snout. 



The ganglion is rather complex in structure. It has a central and somewhat 

 ventral mass of fibers surrounded on all sides by nerve cells and fibers mingled. There 

 are two centers composed each of cell areas surrounding a fibrous mass; these seem to 

 be associated with fibers connected with the sensory epithelium of the snout and they 

 resemble slightly the olfactory areas of certain Invertebrate brains. 



The dorsal nerve trunk Is not cellular. The ventral nerve trunk is thick and 

 broad. Ventrally it is nearly fused with the underlying cells of the body-wall, while 

 dorsally It is bounded by a closely applied muscular layer. The nervous tissue itself 

 is traversed by heavy lines which in part may be merely supportive in function, the 

 lighter strands, both transverse and longitudinal, are branches from the rather abun- 

 dant cells which are for the most part located ventrally. 



(Conlrihulion from the '/.nnlogical Lahoratory of Pomona C.nllrgf.) 



