BRYOZOA, WITH DESCRIPTIONS OF NEW SPECIES. 395 
ther interpretation, which I am inclined to look upon as the true 
one. Dr. Farre observes in his paper, that “in Zunicata the 
tentacles are reduced to mere rudiments at the entrance of the 
respiratory sac, and the cilia are distributed over the surface of 
this cavity, which is in proportion magnified, and is analogous 
to the pharynx of Ciliobrachiata. The more immediate entrance 
to the alimentary canal, thence called mouth, being situated at 
the bottom of this sac, corresponds with the part that I have 
called cardia.” 
This view of the relationship of the parts has, with some modi- 
fications, been generally followed by subsequent writers. In all 
the Ascidians however, there is a well-defined cesophagus, which 
in Clavelina is frequently of great length. Why then should 
the entrance to it be considered to correspond to the cardia in 
Brgozoa? These, as well as the Ascidiw, have a well-marked 
stomach with cardiac and pyloric orifices; in both, too, there is 
a distinct esophagus; then should not the orifice leading to it 
be assumed to be the mouth, or analogous to the mouth in both? 
In the polype a series of respiratory tentacles, in the Ascidie 
the branchial sac, surrounds this mouth; should not these then 
- be considered homologous? The affirmative of this would ap- 
pear to be the natural inference in the first instance. But we 
are referred to the tentacular filaments, at the entrance of the 
respiratory sac, as the true representatives of the tentacles of the 
polype. With the view to ascertain how far this is correct, I 
examined, with much care, Ascidia sordida and Molgula arenosa, 
and found that these tentacular filaments are not anatomically 
connected with the branchial sac, but are developments from the 
tunic. The sac terminates a little way below these filaments, and 
they fringe the inner circumference of the belt of sphincter 
muscles which guard the respiratory orifice. These tentacular 
filaments, then, originating in the tunic, cannot possibly be the 
homologue of the tentacles of the polype, as these undoubtedly 
belong to the alimentary canal ; but are in fact a new develop- 
ment in connection with the sphincter of the tunic, and share its 
function. The tentacles then of the polype and the branchial 
sac of the Ascidian would appear to be homologous ;—unless 
