148 WILLIAM BLAXLAND BENHAM. 
the persistent larval excretory organs or “‘ head kidneys,” the 
lumen of which isintracellular. The “ intertentacular organ,” 
discovered by Farre (7, p. 408) in Alcyonidium and in 
Membranipora, may perhaps be a nephridium. It is 
described and figured as an unpaired ciliated tube, placed at 
the base of the tentacles, opening on a slight cone, and 
through it ova and spermatozoa have been seen to be expelled. 
Otherwise no nephridia are known in Polyzoa. But one of 
the most distinctive features of Phoronis, as compared to the 
Polyzoa, is the presence of a closed vascular system 
containing corpuscles differing from those in the ccelomic fluid 
(Brachiopoda appear to possess different corpuscles in the 
fluids of the various cavities into which the cclom is divided, 
but no system of vessels has been with certainty described). 
No vascular system is found in any of the Polyzoa, and 
on account of their small size there may be no necessity 
for such a system. In regard to the vascular system the 
absence and presence of it does not necessarily point to any 
fundamental difference between two groups, for the Capitellidze, 
as well as other genera amongst the Polycheta, are without a 
separate system of blood-vessels. 
The nervous system in Phoronis is, as already mentioned, 
in an embryonic condition, lying as it does immediately below 
the epidermis, and showing no concentration of nerve-cells to 
form ganglia. In Polyzoa, on the other hand, a subcesophageal 
ganglion is present from which nerves pass to various organs 
and in the larva a structure has been identified by Harmer 
(9) as a supracesophageal ganglion in Pedicellina. 
The gonads in Phoronis are unpaired and lie on the left 
side of the body, ova being developed on one side of the 
longitudinal blood-vessels, and spermatozoa on the other side 
of it. In Polyzoa the glands are paired, and originate on the 
funiculi and body wall. But it is in their development that 
Phoronis and Polyzoa show the most obvious differences. 
In the former Caldwell (5) has shown that the blastopore 
forms not only the mouth but the anus as well, the line of 
¢ “Pine iransaeliooye 
