MUSEUM OF COMPARATIVE ZuOLOGY. 147 



20. Harmer's conclusion, that the ganglion of Phylactolsemata arises 

 exactly as in Endoprocta, is not confirmed. 



21. Tlie "rincr canal" lies at the base of all tentacles. 



o 



22. The circnin<jnil region of the ring canal in Cristatella is in free 

 commnnicatiiin witli the coenoco'l in all stages of development ; and not 

 closed, as maintained by Kraepelin. 



23. The two arms of the lophophore arise independently of each 

 other. Tlieir adjacent surfaces undergo a secondary fusion, which ])er- 

 sists until the inner row of tentacles is about to be formed on the lopho- 

 phore. The two arms then become entirely separate. 



24. The ancestor of Bryozoa probably possessed a U-shaped row of 

 tentacles, encircling the mouth in front, and ending freely behind near 

 the anus. 



25. The tentacles near the mouth are phylogenetically the oldest. 



2G. Both layers of the bud are involved in the formation of the 

 tentacles. 



27. The lophophoric nerves arise as outgrowths of the central ganglion, 

 which make their way into the lophopiiore arms. 



28. The epistome arises as a fold continuous with the wall of the 

 oesophagus below and the floor of the atrium above, and it communicates 

 with the cwnocoel by means of the epistomic canal. 



29. The ccccum of the alimentary tract, wliich occurs only in Ecto- 

 procta, is produced relatively late in the ontogeny by an <int-pocketing 

 of the lower wall of the alimentary tract at the free end nf the pnlypide. 



30. The funiculus migrates (probably with the aid (if ama'boid cells) 

 from the roof of the colony to the margin, or even to the sole. 



31. The " origins" of the retractor and rotator muscles migrate along 

 the radial partitions from roof to sole. The separation of the two mus- 

 cles takes place secondarily as their points of insertion separate. 



32. The parieto-vaginal muscles arise from the coelomic epithelium of 

 the body-wall and polypide. 



33. The disintegi'atinn of the neck of the polypide is begun by a meta- 

 morphosis* of the protoplasm of its cells. The metamorphosed cells 

 break away, leaving the atrial opening. 



34. The part of the body-wall h'ing around the atrial opening arises 

 by proliferation of cells derived from the neck of the polypide. 



35. The ectodermal cells become metamorphosed by an intercellular 

 secretion of small '' (Jallertliallen," which fuse to form the larger ones. 

 Often the contents of more than one cell fuse into a single large mass. 



rA-Mi!i!ii>GF„ .Tunc, 1890. 



