EEPORT ON THE CRINOIDEA. 



121 



varies considerably iu appearance, being relatively thick in some parts and almost totally 

 absent in others ; for I have never found it to extend right across the food-groove as it 

 does in other species (PI. Villa, figs. 4, 5, /;). 



I have cut sections of the arms and pinnules of some half dozen species of Actinometra 

 f nd have found abundant extensions from their axial cords in all cases. The fibrillar 

 tissue generally has a strong yellowish tinge, which renders it easy to follow when it leaves 

 the substance of the skeleton and enters the ventral perisome. Actinometra parvicirra 

 and Actinometra nigra, both from the Philippines, have, however, given me the best results. 

 The axial cord enlarges slightly in the centre of each joint of the ray, arm, or pinnule. 



J a' 



Fig. 5. — Diagrammatic transverse section through the Fig. 6. — Longitudinal section of a pinnule-joint of 



end of a grooved pinnule of Actinometra parvi- Actinometra nigra, x 50. «, axial cord ; a', the 



cirra, x 70. a, axial cord ; a', the branches pro- branches proceeding from it ; c.s., connective tis.'^ue 



ceeding from it ; a.e., ambulacral epithelium ; 6, spaces in the perisome ; e, epidermis ; j, skeleton 



radial blood-vessel ; c.c, cceliac canal ; ci.c, ciliated of the pinnule-joint; W, dorsal ligament; li, 



cup ; C.S., connective tissue spaces in the perisome ; interarticular ligament ; m, muscle. 



j, skeleton of the pinnule-joint ; in', transverse 

 muscle-threads in the water-vessel ; n, radial trunk 

 of the ambulacral nervous system; s.^.c, subten- 

 tacular canal; w, radial water- vessel ; t.b., its 

 tentacular branch. 



and gives ofi" four branches, or occasionally more (PI. LXI. fig. 6 ; woodcuts, figs. 4, 5) 

 One pair of these runs towards the dorsal surface, and breaks up into successive sub- 

 divisions, the last of which are exceedingly fine and can be traced no further (woodcut, 

 fig. 6, a'). The other pair extends towards the ventral side of the skeleton, and passes 

 out of it into the perisome at the sides of the genital glands, where they are continued 

 upwards towards the ventral surface of the arm or pinnule, which may or may not bear 

 a food-groove, according to the part of the body from which it comes. 



In both these species the perisome contains a number of more or less regularly 

 arranged spaces in the connective tissue (woodcuts, figs. 4-7, cs.), and the branches of the 



(ZOOL. CHALL. EXP. — PAET XXXII. — 1884.) I' 1*^ 



