MORPHOLOGY OF BRAIN AND SENSE ORGANS OP LIMULUS. 91 



Fig. 12 a.— Outer end of a cuticular caual of the inner mandibular gusta- 

 tory buds. a. In longitudinal section, b. Seen from above, c. Gustatory 

 canal (outer end) from the chelae. 



Fig. 12 d. — Surface view of the outer end of a sensory bud of canal, from 

 the thorax. 



Fig. 12 e. — Same view of olfactory bud of canal from olfactory organ of 

 female. 



Fig. 12 f. — Same of male. All of Figs. 12 a — d drawn to same scale. 



Fig. 13. — One of the node-like swellings in the cuticular canals seen in 

 Fig. 1 much enlarged, and showing the chitinous tubule within and the spiral 

 fibre. 



PLATE 2. 



Fig. 14. — Isolated chitinous tubule from the gustatory buds of the mandi- 

 bles, showing the thin, granular, protoplasmic investment, with the spiral 

 lines. Treated with caustic potash. 



Fig. 15. — Isolated ganglion-cell from the centre of a gustatory bud. flert- 

 wig's mac. fluid, 5 days. 



Fig. 16. — Chitinous tubules from the mandibular gustatory buds. In a 

 the tubule is stained dark by the acetic acid carmine, and is surrounded by 

 two sinuous, refractive and colourless fibres, b shows the coiled tubules that 

 are frequently found in the mandibles. 



Fig. 17. — Longitudinal horizontal section of the median olfactory nerves 

 and olfactory lobes of a young Limulus about 4 inches long. The lateral 

 olfactory nerves, /. ol. «., which bend outwards beneath the olfactory organ, 

 are cut transversely. X 90. 



Fig. 18. — Outline of the fore-brain, olfactory organ, and nerves, of an adult 

 female Limulus. x 4. 



Fig. 19. — Surface view of the olfactory organ of an adult female, showing 

 the distribution of the cuticular canals leading to the olfactory buds. x 15. 



Fig. 20. — Longitudinal section through the base of the lateral olfactory 

 nerve, showing the ommatidia-like clusters of cells with their refractive, rod- 

 like thickenings, x 200. 



Fig. 21. — Cross-section of the adult olfactory organ. The outer layers of 

 the cuticula have been removed, x 46. 



Fig. 22. — Cross-section of the olfactory organ in a young Limulus about 7 

 inches long. Flemming's fluid (strong), x 90. 



Fig. 23. — Portion of the preceding figure still further enlarged. The 

 thickness of the cuticula is not increased in the same proportion, x 550. 



