104 THE VOYAGE OF H.M.S. CHALLENGER. 



tube. It is connected witli 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 benda 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 ofi" 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 lyulchella. 



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 

 like Bathycrinus and Ehizocrinus, which have relatively high radials (PL Vllb. figs. 3-5 ; 

 PL Villa, 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 VIIlj. 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 applies equally well to Actinometra, 

 Rhizocrinus, Bathycrimis, and Pentacrinus. 



According to Perrier,' however, " Le corps ovoide s'implante chez la Comatule adulte 

 sur I'un des planch ers horizontaux de I'organe cloisonne." 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 

 penetre, en s'amincissant toujours, dans I'axe de I'organe cloisonne;" 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 t}'pes. 



The upper part of the stem contains the usual six vessels, five peripheral and one 

 central (PL XXIV. figs. 2, 5 ; PL LVIII. fig. 3). The single axial vessel which represents 

 Perrier's " cordon central " in the larval stem divides when it enters the chambered 



1 Two figures, illustrating these points in Acti7iometra parvicirra, will be found in the Quart. Journ. Micr. Sci., 

 N. S., voh xxi., 1881, pi. xii. flgs. 14, 15. 



2 Crinoideen, loc. cit., p. 317. ^ Gomptes rendus, t. xcviL p. 188. 

 * Comptes rendus, t. xcviii. pp. 445, 446. 



