MORPHOLOGY OF BRAIN AND SENSE 0RC4ANS OP LIMULTTS. 17 



breathed upon. But stimulation with food or 

 ammonia produces no effect whatever. These facts 

 seem to indicate that there is a reflex centre in the chelae for 

 the temperature impulses^ but none for the gustatory ones. 

 A rather hurried examination, however, failed to show the 

 presence of any centre there, unless the few scattered tripolar 

 ganglionic cells found everywhere in the subdermal nerve- 

 plexus can be regarded as such. 



Description of the Organs. — As one might expect 

 after the above experiments, surface views of the chelse show 

 the presence of two kinds of organs. Those of one kind 

 appear as small pores surrounded by a clear halo, and resem- 

 bling, in their arrangement in lines and in every other par- 

 ticular, the gustatory organs on the mandibular spines (figs. 

 10 and 11, g. o.). See section C. The others are less numerous 

 than the first, but larger, and over each canal there is a 

 saucer-shaped depression, from which projects a short blunt 

 spine. A chitinous tubule passes up the wide cuticular canal, 

 and terminates in the spine. The same kind of organ is also 

 found about the bases of the larger mandibular spines. As the 

 first organs are just like those in the mandibular spines, and 

 as no other organs are found near the tips of the chelae, they 

 are without doubt the gustatory organs. The second kind 

 must, in all probability, be the temperature ones. Sections of 

 the chelse, blackened in osmic acid to show the distribution 

 of the gustatory canals (PI. 3, fig. 44), show that they are 

 very abundant along the cutting edge of the chelse, and even 

 more numerous at the flattened apex of the fingers — in other 

 words, just where they are most sensitive to taste, and where 

 they would be most likely to come in contact with foreign 

 bodies. 



The pedal nerve in the propodite, or the next to the last 

 joint, divides into four branches which run along the anterior 

 and posterior margin respectively of each arm of the chelse. 

 Whether this division of the nerve is due to a separation of 

 fibres into nerves, going some to temperature organs and others 

 to gustatory ones, could not be determined. 



VOL. 35, PART 1. — NEV? SER. B 



