54 Cumings — Development of some Paleozoic Bryozoa. 



adult type of structure (Brachiopoda, Mollusca, etc.). The 

 term is here proposed to cover the complicated degenerative 

 metamorphosis of the Ectoproctous Bryozoa (figs. 11-15 and 

 26). During this stage the margin of the reversed mantle 

 fuses with the margin of the extended and. flattened adhesive 

 plate, and the corona, pyriform organ, and larval intestine 

 (where present) degenerate, forming a mass known as the brown 

 body. The secretion of the ectocyst begins at this stage. The 



Figures 26-30. — Formation of the polypide and protoecmm in Phalan- 

 gella (=Tubulipora). (After Barrois.) 



26. An early sedentary stage, showing rudiment of polypide ; 27. Beginning 

 of tentacles and first zooecium (protcecium) ; 28-30. Formation of first mature 

 individual and primary buds, 1 2 and I 3 . 



pol, polypide ; tn, tentacles ; g, globules formed by degeneration of larval 

 organs; R, rectum; z, zocecium ; b, b, primary buds; 6c?, basal disc. 



Figures 26-29 x 55 ; figure 30 x 40. 



retractile disc is invaginated, and becomes the rudiment of the 

 future polypide.* 



The phylembryo (fig. 27) is characterized by the first appear- 

 ance of the lophophore, the secretion in most types of a chitinons 

 or calcareous investment, and the origin of the true alimentary 

 canal. This is the earliest stage capable of fossilization. It 

 closes with the origin of the primary buds. This first zooecium 

 of the colony is called the protoecium, or primary dwelling. 

 The term protcecium, therefore, will not be exactly cognate 



* According to Barrois 2 a paired organ (r.ex, figs. 8-14) shares in the forma- 

 tion of the polypide. On this subject, see Ostroumoff, 21 Vigelius, 46 Oalvet, 5a 

 and Prouho 29 for a different view. See also the interpretation of the metamor- 

 phosis given by Harnier 12 and Sedgwick. 39 



