REPORT ON THE CRINOIDEA. 97 



but he was unable to satisfy himself ujDon this point. The Naples variety of Antedon 

 rosacea, upon which he worked, is about the worst type that could have been chosen 

 for delicate observations of this kind, the quantity and character of the pigment- 

 granules which the lip contains almost totally obscuring the other tissues. 



This pigment-substance is altogether different from the yellow and brown pigment 

 masses so common in all Echinoderms. It is apparently related to tlie calcareous 

 spicules which are so abundant in the under part of the perisome and in the intervisceral 

 connective tisstie. When these have been removed by acid their outlines are seen 

 to be well defined by streaks of pigment-granules, which appear black by transmitted, 

 and yellowish-white by reflected, light. They are especially abundant in the lip, and 

 in some individuals almost entirely conceal the blood- vascular plexus which it contains ; ' 

 while in specimens from other localities, and in Antedon eschrichti, it is scarcely developed 

 at all, and I have found no difficulty in tracing the connection of the plexiform gland 

 with the oral ring. This is very evident in all the other Comatulee, including Antedon, 

 Actinometra, and Promachocrinus, which I have examined, as well as in Pentacrinus 

 (PL LVII. fig. 3 ; PL LXIL). 



The branching tubules depending from the oral ring which much resemble the visceral 

 blood-vessels, open into a dense plexus of more glandular looking tubules that is 

 supported by connective tissue, and extends right round the lip (PI. LVII. figs. 1, 3, 4 ; 

 PL LIX. fig. 5 ; PL LX. figs. 1, 2, i—lp). 



It is connected with (l) the ventral branches of the plexiform gland (PL LVII. 

 fig. 8, xv) ; (2) with the genital vessels of the rays (PL LX. figs. 1, 2, gv) ; and (3) with 

 some of the intervisceral vessels (PL LVII. figs. 1, 3, 4 ; PL LX. figs. 2, 3, 5, ih ; PL LXIL). 

 These last form an extensive network over the coiled digestive tube, and are also directly 

 connected with the plexiform gland (PL LVII. figs. 2, 5 ; PL LVIII. fig. 6, ih). This 

 labial plexus is most abundantly developed beneath the south and south-east portions of 

 the peristome, i.e., in the neighbourhood of the left posterior ambulacrum. It lies 

 between the hind-gut forming the last coil of the digestive tube, and that part of the 

 capacious fore-gut which lies between the two lateral ambulacra of the right side. It is 

 always pretty sharply defined from the surrounding connective tissue, and is usually a some- 

 what prominent object in a well-stained section which is examined with the naked eye or a 

 simple lens. This is partly owing to the relatively thick walls of its component tubules, and 

 partly to the delicacy of the connective tissue holding them together. Its relations are easily 

 made out by the study of series of tranverse and longitudinal sections through the disk. 



It is not very specially developed beneath the origins of the anterior and antero- 

 lateral ambulacra, the jilexiform genital vessels of which may be traced into it ; though 

 it is somewhat denser on the left (east) than on the right side, where it is connected 



1 I Lave found the same equally impracticable pigment in the disk of Adhiomctra peclinata from Singapore, and also 

 in some individuals of Actinometra parvicirra from Bohol, although others from the same locality are totally devoid of it. 



(ZOOL. CHALL. EXP. PART XXSII. — 1884.) li 13 



