146 BULLETIN OF THE 



like process of cells is given off to form median buds. Between these 

 two extreme types, intermediate conditions occur. 



7. The alimentary tract is formed by two out-pocketings of the lumen 

 of the bud in the median plane, one forming the oesophagus, the other 

 the rectum and stomach. The blind ends of these two pockets fuse, and 

 thus form a continuous lumen. 



8. The central nervous system arises as a shallow pit in the floor of 

 the atrium ; the pit becomes closed over by a fold of the inner layer 

 only of the polypide, which thus forms a sac, the walls of which become 

 the ganglion. 



9. The kamptoderm arises by the transformation of the columnar 

 epithelium of the two layers of the wall of the atrium into pavement 

 epithelium. 



10. The funiculus arises from amoeboid cells derived from the coelomic 

 epithelium. 



11. The retractor and rotator muscles arise together from the coelomic 

 epithelium of both body-wall and bud, and in the angles formed by the 

 radial partitions and the body-wall. 



12. The wall of the colony grows by cell proliferation at its margin. 



13. The radial partitions arise as follows : certain muscles of the 

 muscularis at the margin of the colony leave the latter, and are carried 

 into the ccsnocoel, taking with them a covering of coelomic epithelium. 



14. Budding in Cristatella presents conditions transitional between 

 direct and stoloniferous budding. 



15. Throughout the group of Bryozoa, the youngest and next older 

 buds are intimately related, and the place of the origin of the younger 

 buds relatively to the older is determined by a definite law. 



16. Cristatella differs from Alcyonella in possessing a region of the 

 colony-wall, — the tip of the branch, — which grows independently of 

 the polypides. 



17. Each of the layers of the younger bud arises from a part of the same 

 cell mass as that which gave rise to the corresponding layer of the next 

 older bud. 



18. The digestive epithelium and the nervous tissue are both derived 

 from one and the same layer of cells, the inner layer of the bud. 



19. The alimentary tract of Cristatella at an early stage is similar to 

 that of a young Endoproct. 



