1914 Pomona College Journal of Entomology and Zoology, Vol.VI, No.4j Dec. 



Some Points in the Nervous System of 

 a Large Deep Water Crab 



WILLIAM A. HILTON 



During the summer of 1914 several living specimens of the large 

 crab Loxorliyuchns yraudis Stimp. were obtained at Laguna Beach. 

 One of these was kept for some time in a tank of sea water, and 

 its general movements were observed as it walked about on the 

 bottom or attacked the sharks or other fish in the aquarium. Its 

 movements were slow and its senses seemed not very acute in this 

 situation. 



A gross and microscopical examination of the nervous system 

 gave much the appearance of these organs in other decapods, but 

 the remarkably small size of the brain or head ganglion was espe- 

 cially noticeable. The nerveS^ connected with this ganglion were 

 long and slender. The optic was large, the tegmental a little 

 smaller and the first antennal about as large as this last. Closely 

 associated with the optic was the small oculomotor, and near the 

 connectives the small second antennal. Other small nerves were 

 connected with the brain, whose courses were not traced, including 

 a pair of small frontal nerves. 



The connectives with the thoracic-abdominal ganglion were long 

 and slender, with each its small ganglion a short distance from the 

 brain. A cross connection between these connectives was not seen. 

 It may have been broken in the dissection. 



The thoracic-abdominal ganglion has many nerves connected 

 with it, as shown in the figure; the largest of these were traced to 

 the legs and upper thoracic appendages. The legs are large and 

 heavy and the nerve trunks in them are large; their combined bulk 

 would probably be many times that of the ventral ganglion. 



So far as studied, the internal arrangement of tracts and cells 

 does not differ materially from the classic descriptions of Bethe In 

 another species. One thing especially noteworthy Is the fact that 

 the nerve cells do not seem especially large, nor are the large ones 

 numerous. 



