104 THE VOYAGE OF H.M.S. CHALLENGER. 
tube. It is connected with the plexiform gland proper by numerous intervisceral 
vessels, which pass both above and below the fore-gut so as to completely surround it. 
The plexiform gland proper bends directly forwards as soon as it enters the visceral 
mass, lying at first a little way from the right end of the gullet, but ultimately comes to 
be close to its anterior end. 
This is more nearly in the median longitudinal plane of the disk, so that the 
plexiform gland lies between the gullet and the first or outside coil of the gut; and as in 
Actinometra pulchella, the glandular structure passes directly into the labial plexus at the 
right angle of the mouth.’ It does not therefore, as in the more regular forms, directly 
give off the cesophageal bundle, being only in connection with it by the intervisceral 
vessels which encircle the gullet; but it is the centre for all the vessels of the right and 
anterior sides of the disk, just as the corresponding structure is in Actinometra pulchella. 
The plexiform gland diminishes gradually in size when it has passed out of the visceral 
mass into the central funnel within the radials; and it begins to lose its glandular, more 
or less lobulated appearance (Pl. XXIV. fig. 9, X). This is retained longer in forms 
hike Bathycrinus and Rhizocrinus, which have relatively high radials (Pl. VIIb. figs. 3-5 ; 
Pl. VIIa. fig. 7—x). Vascular cavities begin to appear in it and group themselves into 
an inner set surrounded by a ring of five vessels, which are radially disposed. These 
expand within the basals into the chambers of the chambered organ (Pl. VIIb. fig. 2 ; 
Pl. XXIV. figs. 6-8; Pl. LVIII. figs. 1-3—ch). Ludwig has given an excellent account 
of this connection in Antedon rosacea,? which apples equally well to Actinometra, 
Rhizocrinus, Bathycrinus, and Pentacrinus. 
According to Perrier,’ however, “Le corps ovoide s’implante chez la Comatule adulte 
sur l’un des planchers horizontaux de Vorgane cloisonné.” In this, as in the former case, 
I am at a loss to make out Perrier’s real meaning. For he admits in a later communica- 
tion’ that the ovoid gland or axial organ terminates below “en un tube conique qui 
pénétre, en s’amincissant toujours, dans l’axe de Vorgane cloisonné ;” and that this tube 
is the upward continuation of the cellular “ cordon” in the centre of the larval stem. 
If, however, he intends to deny the communication of the cavities of the chambers 
with those of the plexiform, or, as he calls it, the “ovoid” gland, I must totally disagree 
with him. For I have the most satisfactory evidence of this connection in my series 
both of horizontal and of vertical sections through these structures in Pentacrinus decorus, 
and also in other types. 
The upper part of the stem contains the usual six vessels, five peripheral and one 
central (Pl. XXIV. figs. 2, 5; Pl LVIIL. fig. 3). The single axial vessel which represents 
Perrier’s “cordon central” in the larval stem divides when it enters the chambered 
* Two figures, illustrating these points in Actinometra parvicirra, will be found in the Quart. Journ. Micr. Sci., 
N.S., vol. xxi., 1881, pl. xii. figs, 14, 15. 
* Crinoideen, loc. cit., p. 317. 5 Comptes rendus, t. xcvil. p. 188. 
* Comptes rendus, t. xeviii. pp. 445, 446. 
