394 MR. HANCOCK ON THE ANATOMY OF THE FRESHWATER 
or maturity become attached to that side of the cell which is con= 
nected with the substance sustaining the polypidom. And here 
they remain fixed, indicating the track of the various branches of 
the Bryozoon 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 adhering 
to the surface of its attachment. 
Having now gone through the details of the anatomy and de- 
velopment of the freshwater Bryozoa so 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 mus- 
cular system, but likewise by the digestive apparatus ; and by 
the bright, pellucid, horny character of the external polypidom. 
Tt 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 Ascidic 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 ano- 
the long cilia that clothe its surface. While watching one in this state under 
the microscope, I observed it gradully elongate itself and pass with a slow gliding 
motion to the top of the cell; then forcing its way through the previously closed 
orifice, and passing into the surrounding fluid, commenced to rotate with extra- 
ordinary velocity: in an instant after this its enveloping membrane was torn 
open and cast aside, and the little being, a broadly ovate gemmule, dashed at 
once beyond the field of view. It afterwards kept moving about in various 
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 
alight traces of the retractor muscles remaining. 
