ANATOMY OF HOLOTHURIANS. 213 
testine. A fluid containing nucleated cells fills both the 
pseudo-hemal and water-vascular canals, 
Holothuria floridana Pourtales is a large, dark-brown 
sea-cucumber, with the feet scattered irregularly over the 
body, and with smaller tentacles than in Pentacta, which is 
abundant just below low-water mark on the Florida reefs, 
and grows to about fifteen inches in length. The aliment- 
ary canal is filled with foraminifera and pieces of shells, 
corals, etc.; it is about three times the length of the hody, 
and ends in a much larger coecum than that of Pentacta. 
There are two widely separated branches of the ‘“‘ respira- 
tory tree,’’ one being free, and the other, tied to the body- 
walls by thread-like muscular attachments, extends to the 
pharynx. The pharynx is calcareous, while in Pentacta it 
is muscular. On the madreporic body is a group of about 
thirty pyriform stalked bodies, the longest, including the 
stalk, about a quarter of an inch in length. Succeeding 
these bodies, and situated on the madreporic canal, leading 
to the ring-canal, are a large number of Polian vesicles, the 
largest one an inch in length. The duct passes spirally 
nearly round the cwsophagus, and empties into the ring- 
canal by the ducts nearly a quarter of an inch apart. In 
connection with the tentacles or branchiz are twenty long, 
slender tentacular ampulle, not present in Pentacta and 
Thyone. The ovarian tubes are very small, some enlarging 
and bilobate at the end. 
Closely allied in external form to Holothuria floridana, 
though belonging to a different family (including Pentacta), 
is Thyone briareus (Lesueur), which lives just below tidal 
marks, from Long Island Sound to Florida. In this genus 
the ambulacral feet are not arranged in rows, but scattered 
over the surface of the body. This species is very common, 
and as it is more accessible to the student than any other of 
the sea-cucumbers, we give some points in its anatomy as 
compared with Pentacta, with which it is more closely allied 
than to Holothuria. In a specimen about eight centi- 
metres (three inches) long the intestine is over two metres 
(about seven feet) long, the esophagus opening into an 
oval stomach less than an inch in length. The tentacles 
