DESCRIPTION OF PLATE XII. 



Illustrating the aisatomy of the ComatulcB. Figs. 9, 10, and 13 are 

 copied from Ludwig. The following letters denote the same parts in all 

 the figures : 



a. Axial cords of the skeleton ; a. the branches proceeding from 

 them ; ce. oesophagus ; oe. b. (Esophageal bundle of vessels ; a. g. am- 

 bulacral groove ; a. m. muscle branches from the axial cords ; a. t. anal 

 tube ; ^1, 5o, -ffg, &c., first, second, and third brachials, &c. ; c. con- 

 nective-tissue network in the ccelom ; c. c. coeliac canal ; c. co. circular 

 commissure in the first radials ; cd. centrodorsal piece ; ch. chambers 

 of the chambered organ ; ci. cirrhi ; ci. c. ciliated cups ; ci. v. cirrhus 

 vessels ; c. s. connective-tissue spaces in the perisome ; cv. circum- 

 visceral coelom ; Dj, I).., D^- first, second, and third distichals ; ff. c. 

 genital canal ; i. h. intervisceral blood-vessels ; io. intervisceral ccelom ; 

 /. b. lateral branches of the water-vessels ; I. p. labial plexus ; m. 

 muscles ; m'. transverse muscle threads in the water-vessels ; N. fibril- 

 lar sheath of the chambered organ; p.j. pinnule joint ; R^, R.2, i?3- 

 first, second, and third radials ; r. rosette ; sa. sacculi ; s. t. c. subtenta- 

 cular canal ; si/z, syzygy ; T. tentacles ; w. p. water-pore ; w. t. water- 

 tube. 



Fig. 9. — Transverse section of a pinnule of a sexually mature Anttdon 

 IlichncUii. $ X 50. 



Fig. 10. — Transverse section through the ventral perisome of an arm of 

 Anfedon Eschrichtii. x 75. 



g. c'. Genital cord ; x. coagulum in radial blood-vessel. 



Fig. 11. — Transverse section through the end portion of a grooved 

 pinnule of Adinometra polymorpha. X 70. 



, Fig. 13. — Transverse section through an ungrooved pinnule of the same 

 jinimal, $ x 50. 



I. t. Lateral trunks connecting the subtentacular and ccEliac canals. 



Fig. 13. — Diagram of the distribution of the axial cords within the 

 calyx of Comatida, showing their origin in the fibrillar envelope of the 

 chambered organ. 



Fig. 14. — Longitudinal vertical section through the body of Aciinometra 

 poli/morph((. X 10. Diagrammatic. Since the position of the mouth is 

 interradial, the section traverses the joints of a ray behind the mouth, but 

 does not pass along the corresponding ambulacral groove, which only 

 reaches its destination after a circuitous course round the margin of the 

 disc, and is cut somewhat obliquely. 



Fig. 15. — Vertical transverse section through the centre of the body of 

 a somewhat larger specimen, x 7. Diagrammatic. Two of the rays 

 and four ambulacral grooves are cut rather obliquely. The section is 

 represented as seen from its anterior side. 



