1873.] 309 . [Morse. 
the sand, while the peduncle lay embedded in the sand. The thorax 
lived for a few days in a weak condition, the sete moving feebly, and 
the dorsal plate slightly oscitlating. This portion finally turned 
black, and as one after the other perished in this way, I removed 
them from the vessel, in order that their decomposition might not vi- 
tiate the water, and thus imperil the lives of the survivors. 
Several days after they had all been removed in this way, curiosity 
led me to turn up the sand, to find the condition of the peduncles, 
and judge of my astonishment at finding the perivisceral fluid con- 
tained in the peduncular cavity still rapidly circulating in several, 
though the region at which the separation had occurred was _ black- 
ened by decomposition. In a few days more this circulation ceased, 
and decomposition envolved all parts. Here we have the most com- 
plete relation between the dissolution of this Brachiopod and that 
of the Annelid described by Dr. Williams. 
Opinions of Authors concerning the Relations of the Brachiopoda. 
Naturalists are sufficiently well acquainted with the relations re- 
peatedly pointed out, as existing between the Brachiopoda and Poly- 
zoa,! and there is no need of again repeating them here. 
It is also a matter of history that the Polyzoa were placed with the 
Mollusca solely on the relations which were supposed to exist between 
them and the Tunicates, and afterwards the relations recognized be- 
tween the Polyzoa and the Brachiopoda. 
Again, there can be no question that at the outset the association 
of the Tunicata with the Mollusca arose from the relations supposed 
to exist between the external sac or tunic, with the two apertures of 
the one, and the shells and syphons of the other. Aristotle? dwells 
on this resemblance where he says, in speaking of them as Mollusca, 
“They are the only kind whose whole body is enclosed in the shell, 
and that shell of a substance between true shell and leather. They 
are attached to the rocks by their shell. They have two separate 
1Jn the affinities of the Polyzoa with the Vermes, the curious genus Phoronis 
offers an important link. Claparéde thinks the affinities of Phoronis are with the 
Gephyreans on the one hand, and the Polyzoa on the other. Kowalevesky has 
discovered that the larva of Phoronis is an Actinutrocha, and possibly the young 
Sipunculoids that Schneider saw resulting from a transformation of Actinotrocha, 
are early stages of Phoronis. Certainly no one studying the characters of Phoro- 
nis and Crepina can fail to see. many very intimate relations between these forms 
and the hippocrepian Polyzoa. 
2 Fourth book of ‘‘ History of Animals.” 
