Freshwater Bryozoa, with descriptions of new Species. 195 
ova on maturity become attached to that side of the cell which 
is connected to the substance sustaming the polypidom. And 
here they remain fixed, indicating the track of the various branches 
of the Bryoozon long after its decay and disappearance in autumn. 
The free branches however must scatter their eggs. Most likely 
in Fredericella, too, they are dispersed, and borne away by the 
currents on the destruction of the polypidom, which is very freely 
branched ; and in no instance have I seen its eggs left adhermg 
to the surface of its attachment. 
Having now gone through the details of the anatomy and de- 
velopment of the freshwater Bryozoa as far as I have been able 
to study them during a very short but laborious investigation of 
the subject, it is quite evident that these animals are as highly 
organized as the marine Ascidian polypes. Plumatella and Fre- 
dericella certainly show some interesting deviations from that 
type; but in Paludicella we perceive an almost complete resem- 
blance to it ; proving the close affinity that exists, and the pro- 
priety of uniting the whole into one group. The approximation 
of this genus to the marine forms is evinced not only by the 
muscular system, but likewise by the digestive apparatus ; and by 
the bright, pellucid, horny character of the external polypidom. 
It is also equally evident that the organization of this group is 
very much above that of the typical Radiata. This Professor 
Allman has already clearly demonstrated; and yet perhaps we 
ought to hesitate before removing the Bryozoa into the subking- 
dom Mollusca as proposed by this naturalist. 
The immediate relationship of these animals to the Ascidie is 
too obvious to be called in question,—a relationship which has 
long been acknowledged, though the homology of the parts does 
not appear to be correctly understood; at least it will bear 
another interpretation, which I am inclined to look upon as the 
true one. Dr. Farre observes in his paper, that “in Tunicata 
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 im 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 
modifications been generally followed by subsequent writers. In 
all the Ascidians however, there is a well-defined cesophagus, 
directions and evinced great activity, cilia densely clothing it from end to 
end. The cell after the escape of the gemmule continued gaping; and the 
polype, which before was indistinctly visible, had now quite disappeared, 
nothing but slight traces of the retractor muscles remaining. 
13* 
