REPORT ON THE CRINOIDEA. 121 
varies considerably in 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. VIIIa. figs. 4, 5, x). 
I have cut sections of the arms and pinnules of some half dozen species of Actinometra 
and 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 mgra, 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, 
== 
Fic. 6.—Longitudinal section of a pinnule-joint of 
Fic. 5.—Diagrammatie transverse section through the 
Actinometra nigra, x 50. a, axial cord ; a’, the 
end of a grooved pinnule of Actinometra parvi- 
cirra, x 70. a, axial cord; a’, the branches pro- 
ceeding from it; a.e., ambulacral epithelium ; 2, 
radial blood-vessel ; c.c., celiac canal ; ci.c., ciliated 
cup ; ¢.s., connective tissue spaces in the perisome ; 
branches proceeding from it ; ¢.s., connective tissue 
spaces in the perisome ; e, epidermis ; 7, skeleton 
of the pinnule-joint ; 7d, dorsal ligament; li, 
interarticular ligament ; m, muscle. 
j, skeleton of the pinnule-joint ; m’, transverse 
muscle-threads in the water-vessel ; , radial trunk 
of the ambulacral nervous system ; s.¢.c., subten- 
tacular canal; w, radial water-vessel; ¢.0., its 
tentacular branch. 
and gives off four branches, or occasionally more (Pl. 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, ¢.s.), and the branches of the 
(ZOOL. CHALL, EXP,—PART XXXII,—1884.) 16 
