﻿312 CONTRIBUTIONS TO THE NATURAL HISTORY 



Fi°\ 10. The upper arch of a radiating tube, in a position somewhat different from that in Fig. 7 ; in Fig. 7, the tube 

 is in perfect profile, so that its inner cavity, c, contrasts closely with its walls, b ; while, in Fig. 10, the tube is seen from 

 above, a indicating its cavity, b and c its margins. 



Fig. 11. A sensitive bulb in its normal connection with the vertical radiating tube, e, and the circular tube, b,b, much 

 enlarged ; a representing the nervous cord ; c, the sensitive bulb ; and d, the part of the tentacles with the eye-specks 

 at their base. See page 268. 



Fig. 12. The sensitive bulb seen from below, slightly enlarged. 



Fig. 13. The sensitive bulb in a position similar to that of Fig. 11, but the tentacles hanging downwards ; in such a po- 

 sition the connection of the radiating tube, b, with the circular tube, a, a, is very obvious. The eye-specks are indistinctly 

 seen through the tentacles, c, c. 



Fig. 14. The sensitive bulb in its connection with the lower partition, seen from below, the tentacles stretching hori- 

 zontally ; a, a represent the eye-specks; b, b, the tentacles slightly elongated, while their base, c, c, is considerably 

 stretched ; d, d, the ganglion of the bulb into which the nervous cord, /,/, penetrates ; the dark cones arising from this 

 ganglion point to the centres of the eye-specks ; e, e being the circular chymiferous tube rising behind the bulb to unite 

 with the vertical radiating tube ; g, g, the muscular lower horizontal partition. 



Fif. 15. The sensitive bulb raised and seen somewhat from the side, most of the tentacles raised upwards, while the 

 lateral ones hang downwards. In this position, which the sensitive bulb assumes chiefly when the body is contracted, the 

 bulb itself is folded into three lobes, one corresponding to the largest middle tentacle, the lateral lobes being formed by the 

 tentacles of the two sides. 



Fig. 16. A view similar to that of Fig. 14 ; a being the eye-specks ; b, the circular tube ; c, the nervous cord ; d, the 

 elongated tentacles ; and e , the pigment cones of the ganglion. 



Fig. 17 represents the lower margin of the body with two sensitive bulbs, one on the right, seen from without; one 

 on the left, seen from within ; a being the circular tube; b, the nervous cord; c, the lower muscular partition ; d, d , the 

 vertical radiating tubes ; /, the inner vertical muscles ; and e, the outer wall of the body. 



Fig. 18. The central digestive cavity (see p. 260) ; a being the mouth shut ; b, b, the transparent tissue forming the outer 

 wall of this cavity ; r, c, the main stems of the tentacles of the mouth ; d, d, their terminal branches ; e, e, the radiating 

 tubes arising from the upper corners of the digestive cavity ; /, the upper wall of the cavity ; g, g, eggs imbedded in 

 the surface of the digestive sac. 



Fig. 19. The digestive cavity seen from above, with its four radiating tubes, a, a; b being a temporary swelling at 

 the base of one of the radiating tubes; r, the centre of the cavity; d, d, its walls. 



Fig. 20. A more enlarged view of the same, also seen from above ; a, a being the radiating tubes, somewhat dilated 

 at their base, b, b, containing granules which circulate to and fro from the central cavity into the radiating tubes ; c, c, 

 bunches of eggs upon the outer surface of the digestive sac. 



Fig. 21. Mouth entirely open, seen from below, allowing a sight into the cavity of the digestive sac; a, a being the 

 margin of the mouth ; b, the main stem of the tentacles of one of its angles ; c, c, the tips of the tentacles ; d, the folds 

 of the inner surface extending into the base of the radiating tubes; e, e, brown cells lining the inner surface of the cavity. 



Fig. 22. The central digestive cavity in its most contracted state ; a, a being its prominent angles, corresponding below 

 to the four bunches of tentacles, and above to the base of the four radiating tubes ; b, the central cavity reduced to the 

 utmost by contraction ; c, the folds between the prominent angles of the sac. 



Fig. 23. The mouth, with its tentacles and bunches of eggs surrounding the central cavity, seen from below. The 

 mouth, a, with its four folds, c, and its transparent margin, b, is figured as complete ; but only two bunches of tentacles, 

 d, d, and two bunches of eggs,/,/, are fully represented ; e, e indicate the tips of the tentacles. 



Fig. 21. A terminal branch of the tentacles, to show their irregular terminal divisions. 



Fig. 25 represents such a branch more highly magnified, to show the large internal cells, a, a, and the coating of 

 smaller cells, b, b, surrounding them ; c, c being the terminal nettling cells. 



Fig. 26 represents another terminal branch of tentacles less magnified, but showing, also, distinctly the large internal 



