MUSEUM OF COMPARATIVE ZOOLOGY. 147 



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

 exactly as in Endoprocta, is not confirmed. 



21. The "ring canal" lies at the base of all tentacles. 



22. The circuraoral region of the ring canal in Cristatella is in free 

 communication with the ccenocoel in all stages of development ; and not 

 closed, as maintained by Kraepelin. 



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

 other. Their adjacent surfaces undergo a secondary fusion, which per- 

 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. 



26. 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 lophophore 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 ccenocoel by means of the epistomic canal. 



29. The coecum of the alimentary tract, which occurs only in Ecto- 

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

 of the lower wall of the alimentary tract at the free end of the polypide. 



30. The funiculus migrates (probably with the aid of amoeboid 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 ccelomic epithelium of 

 the body-wall and polypide. 



33. The disintegration 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 lying 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 " Gallertballen," which fuse to form the larger ones. 

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



Cambridge, June, 1890. 



