Quarterly Journal of Microscopical Science (Volume 35) (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: 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 chelee show the presence of two kinds of organs. Those of one kind appear as small pores surrounded by a clear halo, and resembling, in their arrangement in lines and in every other particular, 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 chelae, 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 chelae, 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 t...