REPORT ON THE CRINOIDEA. 127 
these plates. It appears to me very probable that this may also be the case in 
Thaumatocrinus (Pl. LVI. figs. 1-4), @.e., that the primary cords pass right up out of the 
basals into the interradials and then divide, so that the secondary cords would enter the 
sides of the radials as in Bathycrinus, instead oftheir inner ends as in Pentacrinus and 
Comatula. 
G. Tue Saccuni, AND THE CoLourinc Marrrrs. 
The nature and functions of the sacculi are as much a puzzle to me now as they were 
when I first began to study the Crinoids in 1875; and I have nothing to add to the 
observations of Wyville Thomson and Perrier on their appearance in the living animal, 
both larval and adult. Colourless during life, they become strongly tinged after death 
by the pigment set free from the perisome. Their occurrence in the wall of the digestive 
tube in Antedon rosacea was first noticed by Ludwig; and [ have found them in the 
very lowest part of the cup of a larva with five cirrus-stumps, just above the chambered 
organ. But this is the only species known to me which presents this peculiarity. In all 
other types in which the sacculi occur at all, they are invariably limited to the immediate 
neighbourhood of the water-vessels. Abundant in most species of Antedon, they 
never occur in Actinometra, and I suspect that Ludwig’s reference to their presence in 
this genus is due to an oversight.1. At any rate I have not been able to find them in 
Actinometra trachygaster and Actinometra bennetti, the two species which had come 
under his observation. 
They vary considerably in distribution among the other genera of Comatule. I 
have not succeeded in finding them in Thaumatocrinus, while they are but scantily 
developed in the three species of Atelecrinus. Eudiocrinus indivisus and Eudiocrinus 
atlanticus have them in abundance; while there are few in Hudiocrinus varians and none 
in Eudiocrinus semperi or in Hudiocrinus japonicus, so far as I have been able to make 
out. Promachocrinus kerquelensis has them on the pinnules, but they are very scanty or 
absent elsewhere. Neither have I found any in a small series of sections through a 
Holopus-arm ; and though structures of the same nature occur sparingly in Pentacrinus, 
Rhizoerinus, and Bathycrinus, they are but poorly developed and irregular in their 
occurrence. 
In some species of Actinometra individual vesicular bodies resembling the elements of 
the sacculi are scattered through the ventral perisome; but there is no regular arrange- 
ment of them into groups at the sides of the ambulacra as in the endocyclic Crinoids. 
When the ambulacra are plated, as in many tropical Antedons, the sacculi are lodged 
between the successive side plates, the front edges of which are notched for their reception 
(PL LIV. figs. 4, 6-9); while they occupy little pits in the large plates which cover the 
1 Zeitschr. f. wiss. Zool., Bd. xxix., 1877, p. 59. 
