MORPHOLOGY OF BRAIN AND SENSE ORGANS OF LIMULUS. 25 



Termination of the Nerves. — On the terminal joints 

 of the exopodites to the abdominal appendages sense buds 

 like those in the olfactory organ are very numerous ; and as 

 there is little surrounding tissue, one can peel off the cuticle 

 organs, together with the after maceration in nitric acid. 

 When such a preparation is placed in dilute glycerine and 

 examined from the inner surface, the nerve-plexus underlying 

 the organs can readily be seen. Branches like those shown in 

 fig. 9 are seen anastomosing with one another in a most 

 intricate manner. In the olfactory organs one cannot obtain 

 such instructive surface preparations, owing to the crowding 

 together of the sense buds and the abundance of connective 

 tissue and blood-vessels ; but sections and isolated sense buds 

 show clearly that the plexus is much the same as in the ab- 

 dominal appendages, only a little denser. In the olfactory 

 region the larger branches of the plexus usually lie a little 

 below the organs, but they may lie directly on their inner 

 surfaces, or may be squeezed in between adjacent buds. In 

 some cases large branches seem to penetrate into the interior 

 of the organ, but such appearances may be deceptive owing to 

 the crowding of the organs. 



The nerves actually connected with the organ are delicate, 

 transparent, nucleated filaments, easily overlooked; they spring 

 from the coarse strands and spread over the surface of the 

 buds, as shown in fig. 9. I could discover no uniformity in 

 number, or any of that drawing out of the cells often seen 

 where nerves unite with sense organs. They can be followed 

 a short distance as very faint, but rather wide fibrillated bands, 

 some of which appear to dip down between the cells toward 

 the central cavity. Occasionally one sees an irregular, poorly 

 defined body containing several nuclei, from which arise a few 

 nerve strands that spread out over the surface of the bud (fig. 

 9, g. c). They sometimes contain a single large multipolar 

 ganglion-cell, with dark granular protoplasm and a clear 

 nucleus. The exact method in which the nerve strands ter- 

 minate is very difficult to determine. 



About the neck of the buds are numerous fibrous strands 



