Freshwater Bryozoa, with descriptions of new Species. 191 



sketched out within the cell of the parent, its own chamber ra- 

 pidly forms, and in the course of a day or two, the muscles in 

 connexion with the orifice being added, the fresh-born member of 

 the community bursts from the extremity of its cell, and is ready 

 to take upon itself the work of its own maintenance. 



The development of the bud in Plumatella differs in no respect 

 from that of Fredericella ; and in Paludicella there is no very im- 

 portant deviation, except at the commencement of the process. 

 In this the first apparent step in the growth of a new polype is 

 the preparation of a distinct cell for its reception. If the top of 

 the last-formed cell be carefully examined, even before its tenant 

 is fully grown, the lining membrane may be seen terminating in 

 a blind sac, PI. IV. fig. 4 b', a little below the extremity. Within 

 this extremity will also be observed a membranous sac, I; at first 

 the base of this sac is moulded on the convex blind termination 

 of the lining of the old cell. The convexity however soon fiat- 

 tens and the sac rapidly increases in size, the external horny 

 covering becoming at the same time elongated and attenuated. 

 After awhile, an oval, somewhat opake body, the new bud, fig. 5 m, 

 germinates from the inner surface of the lining membrane, /. 

 This body is attached by its side to the front wall of the cell, and 

 resembles the young bud in Fredericella. A long and very deli- 

 cate membranous sac, fig. 6 d, afterwards the tentacular sheath, is 

 now observed to be forming in contact with and above the oval 

 bud ; whilst from the lower extremity filaments, e, are seen to be 

 produced which form the polype-retractors. From the upper end of 

 the bud, the tentacles, fig. 4 d, soon make their appearance within 

 the lower part of the membranous sheath, i ; at first very short, 

 no more than the scalloped margin of the cup-formed disc ; but 

 rapidly lengthening, fig. 5 a, they soon advance more than halfway 

 up the sheath. The polype-retractors, figs. 4<j & 5 g, by this time 

 are considerably developed, and the retractors, /c, i, of the tube 

 are distinctly visible ; the tube, fig. 4*j, now begins to bulge, and 

 the inverted margins of the orifice are seen within, united to the 

 upper end of the tentacular sheath : the parietal muscles, h, also 

 make their appearance at this time, and the stomach, c, intestine, 

 d, oesophagus, b, and tentacles having all assumed their proper 

 forms, the young animal is ready for protrusion. The buds of 

 Paludicella, however, do not all originate from the extremity of 

 the old cell ; some sprout from the side, and then a slight swell- 

 ing takes place on the inner surface of the tunic. The horny 

 sheath soon afterwards begins to bulge, and an external cell 

 being formed with its lining membrane, an oval bud makes its 

 appearance, and development goes on as just described. 



It has been long known that these animals propagate by eggs 

 as well as buds ; Raspail appears to have described the anatomy 



