Freshwater Bryozoa, with descriptions of new Species. 203 



tella Allmani : a, mouth ; b, oral valve ; c c, oral arms ; d, mem- 

 brane at base of tentacles. 

 Fig. 4. Much-enlarged view of the reproductive organs of Fredericella sul- 

 tana : a a, outer wall of cell ; b b, lining membrane or tunic ; 



c, lower portion of stomach ; d d, ovary ; e, egg imbedded in same ; 

 /, two filaments attached to the lower end of stomach, probably 



connected with the reproductive system ; g, retractor muscles. 

 Fig. 5. Enlarged view of a cell of Plumatella Allmani exhibiting reproduc- 

 tive organs : a, base of oral arms ; b, oesophagus ; c, stomach ; 



d, intestine ; e e', ovary ; f, egg nearly mature, still attached to 

 ditto ; g, an egg just forming likewise attached to ovary ; h h, two 

 filaments attached to the stomach, probably connected with the 

 reproductive system ; i i, the two bundles of retractor muscles ; 

 j, outer wall of cell ; k, lining membrane or tunic. 



Plate IV. 



Fig. 1. Enlarged view of a cell of Paludicella procumbens seen as a trans- 

 parent object, the polype being exserted : a a, outer wall of cell ; 

 b b b, lining membrane or tunic ; c, tubular orifice ; d, membranous 

 cup surmounting ditto ; e, tentacular disc ; /, tentacles ; g, pha- 

 ryngeal swelling ; h, oesophagus ; i, stomach ; j, intestine ; k, en- 

 largement at commencement of ditto ; I, anus ; m, supposed ovary ; 

 n, filament attached to the lower extremity of stomach, probably 

 connected with the reproductive system ; o, polype retractor 

 muscles ; pp, inferior tube-retractors ; q, two fibres of superior 

 tube-retractors ; r r, muscles to prevent the complete inversion of 

 tentacular sheath ; s, tentacular sheath doubled upon itself ; t, pa- 

 rietal muscles; u, end-walls of two cells abutting against each 

 other. 



Fig. 2. Enlarged view of a single cell of P. procumbens with polype re- 

 tracted : a, outer wall of cell ; b, lining membrane of ditto ; c, re- 

 tracted tubular orifice ; d, tentacles ; d' d', tentacular sheath ; e, 

 oesophagus ; /, cardiac orifice ; g, stomach ; h, intestine ; i, enlarged 

 portion of ditto ; j, supposed ovary doubled upon itself; k, filament 

 attached to lower end of stomach, probably connected with repro- 

 ductive system ; 1 1, polype retractor muscles ; m m, inferior tube- 

 retractors ; nn, superior tube-retractors ; o, sphincter muscles for 

 closing orifice ; p, do. do. ; q q, muscles to prevent complete in- 

 version of tentacular sheath ; r, end- wall of cell formed by the 

 tunic exhibiting enlargement in the centre. 



Fig. 3. End of retracted tube of P. procumbens exhibiting the manner in 

 which it folds in. 



Fig. 4. Termination of a branch of P. procumbens comprising two cells in 

 different stages of development : a, outer wall of cell in fourth 

 stage of development ; b, lining membrane of ditto ; b', blind ter- 

 mination of do. do. ; c, place of future orifice ; d, tentacles of 

 polype in state of development ; e, oesophagus ; /, stomach ; g, in- 

 testine ; h, lower reproductive organ ; i, tentacular sheath ; j, po- 

 lype retractor muscles ; k, tube-retractors ; /, new cell in first or 

 earliest stage of development, exhibiting lining membrane and ex- 

 ternal wall ; m, nucleated cells in lining membrane. 



Fig. 5. Two terminal cells of P. procumbens containing buds in different 

 stages of development : a, tentacles of bud far advanced or in 

 fifth stage of development ; a', tentacular sheath ; b, oesophagus ; 

 c, stomach ; d, intestine ; e, anus ; /, lower reproductive organ ; 

 g, polype-retractors ; h, parietal muscles ; i, tube-retractors ; j, tube 



