ANATOMY OF SPHa:iiOTHERIUM. 173 



Fig. 9. Antenna of S. reiicsum, showing the terminal sense-organ, p. The 

 processes in which are the sensory hairs, r, r. The white ring sur- 

 rounding each process. 



Plate XXVIII. 



Kg. 10. A still further enlarged ^iew of the end of the antenna of S. reiusum, 

 showing the sense-organ : the lettering as in fig. 9, PL XXVII. 



11. Diagrammatic longitudinal section of the antennary organ in S. retusum. 



a. Antennai-j nerve, a}, a}, a^. The branches of the nerve, one going to 

 each nerve ending in the terminal point, a^, a^. Nerve-bundles formed 

 of neurospongium. c. Large ovoid cells (blood-corpuscles ?) lying in 

 the connective tissue (t) which surrounds the nerve-bundles, cf. Gang- 

 lion-cells, e. Terminal sense-organs. 



12. A single nerve-bundle, much magnified, a^. Branch of antennary nerve. 



a^. Neurospongium. g. Ganglion-cells, s.h. Sensory hairs sur- 

 rounded by a chitinous cap (c. A.), i. Connective tissue, tr. Trachete. 

 0. Large ovoid cells (blood-corpuscles ?). 



13. Diagrammatic transverse section through the antennary organ, much 



magnified, b. Nerve bundles in section, c. Large ovoid cells (blood- 

 corpuscles ?). s.c. Subcuticular layer of cells, p. Pigment. 



Plate XXIX. 



Fig. 14. Diagram of the tracheal and nervous system of S. obtusum. a. Antenna. 

 an. Antennary nerve, aw. Auditory (?) nerve. c6. Cerebral ganglion. 

 CO. Nerve-commissure, co^ and co^. Nerves joining the two strands of 

 the commissure above and below the oesophagus, e. Eye. ffl, g'2, ff3. 

 The ganglia of the three' first body-segments. gQ,g^. The pairs of 

 ganglia belonging respectively to the sixth and ninth body-segments, 

 g 21. The last ganglion, being the hinder one of the pair belonging 

 to the twelfth segment, n. Nerve arising from the last ganglion, and 

 supplying the accessory appendages of the male, n}, 7i^. Larger nerves 

 to the appendages, n^. Smaller nerve to the penes, n.l. Nerve sup- 

 plying the leg ; one pair arises from each ganglion, n.i. Nerve to the 

 tracheal sac, one pair arising from each ganglion, o. Optic nerve, 

 as. ffisophagus cut through, sn. The sense-organ on the terminal 

 antennary joint, t^, Trachete, arising from the tracheal sac near the 

 middle line, and supplying the viscera, t"^. Tracheae arising from the 

 tracheal sac near the lateral line on either side and supplying the 

 dorsal and lateral muscles, i^. Three large tracheae arising from the 

 first tracheal sac and supplying the head. t 21. The last tracheal 

 sac, being the hinder one of the pair belonging to the twelfth body- 

 -segment. 1, 2, 3. The single tracheal sacs in the first three body- 

 segments. .4, 5, 6, 7, 8, 9, 10, 11, 12. The pairs of tracheal sacs be- 

 longing to the nine posterior body-segments. 



