REPORT ON THE CRINOIDEA. 119 
that they have all the appearance of being true nerves.’ He further ‘deseribes how their 
ultimate subdivisions “ aboutissent a des cellules étoilées, dont chacune se prolonge en 
un fibre musculaire. Des ramifications de ce genre sont également en rapport avec les 
fibres que contiennent les tentacules ambulacraires et dont un grande nombre se tiennent 
dans les papilles sensitives de ces tentacules que Ludwig considére & tort comme creuses.” 
Elsewhere he states that the cords are invested with a sheath of stellate. cells which are 
themselves related to connective-tissue corpuscles, and through these with the ectodermal 
cells of the arm. ‘These statements of Perrier’s are of considerable importance, and 
should his observations be confirmed the nervous nature of the axial cords will, I think, 
be at last admitted, even by those whose scheme of Echinoderm morphology is founded 
upon the archetype of a Stellerid or Urchin. These, however, are formed almost entirely 
upon the left larval antimer, whereas the chambered organ of a Crinoid and its downward 
extension into the stem are formed in the right peritoneal tube. (See Appendix, Note G.) 
The branches from the axial cords of the rays and arms, to which. allusion has so 
frequently been made, vary considerably in their development and distribution. Among all 
the numerous Crinoids, stalked and free, that. 1 have examined, Rhizocrinus is the only one 
in which these branches have not been visible. I see no reason to doubt their existence, 
however; but the genus is one of small size, and is also permanently fixed through life, so 
that one would not expect to find large muscular branches proceeding from the axial 
cords, as in the Comatul and Pentacrinidee which are free or semi-free, and can use their 
arms for the purpose of swimming ; whereas, according to Agassiz,” the movements of 
extension and flexion of Rhizocrinus are but slow and gradual. The branches are also 
poorly developed in the massive and sessile Holopus. But in Bathycrinus, in the 
Pentacrinide, and in the Comatule they are very largely developed, occurring not only 
in the arms and rays but also in the stem and cirri, They vary considerably in their 
extent, some portions of the stem showing them abundantly( Pl. XXIV. fig. 2, ca’), 
while in others they are less numerous. An optical.seetion of two decalcified stem-joints 
of Bathycrinus aldrichianus is shown in Pl. Va. fig. 1. The larger branches of the 
axial cord (ca’) are seen with a low power where the radial spaces render the stem- 
substance more transparent than elsewhere, but this gives no idea of the minuteness and 
complexity of their subdivision, which only reveals itself by the use of a high power. 
In Pentacrinus wyville-thomsoni again I have found these branches to be abundantly 
developed in some stem-joints and almost entirely absent in others (Pl. XXIV. figs. 1-5). 
The fibrillar envelope surrounding the vascular axis is sometimes in immediate contact 
with the reticular tissue which forms the organic basis of the skeleton (figs. 2, 3). But 
in other joints it is closely surrounded by a layer of large pigment bodies like those 
which occur scattered in more or less abundance through the skeletal tissue (fig. 5, 7). 
In other sections again, fibrillar extensions of the central axis pass outwards from it 
1 Comptes rendus, t. xcyii. p. 188. 2 Tl. Cat. Mus. Comp. Zodl., No. viii. p. 29. 
