BRYOZOA FROM ZANZIBAR. 505 



Frequently a liydroid is growing over the surface. This seems 

 to be a species of Clava and may be the same species as one 

 growing in Holoporella columnaris B., and H. pigmentaria Waters, 

 in which it may pass through several layers of zooecia. Sections 

 showed that the stolons were spread under the H. columnaris, 

 indicating that the growtli of the Holoporella occurred over 

 established colonies of Clava round which the Holoporella formed 

 calcareous tubular walls *. 



(1) S. nivea belongs to a group in which all the species 

 have a wide sinus or arc, the surface is perforated as is 

 also the ovicell, there are quite small oral glands or but very 

 moderate sized ones. The opercula have the muscular attach- 

 ment close to the border and fairly near to the distal end. This 

 group I referred to f as including the types of Schizoporella, 

 and belonging to it are S. sanguinea Norm., S. linearis Hass., 

 S. harmsworthii Waters, S. auriculata Hass., S. galeata B. ? etc., 

 and a new species from S. Africa. Levinsen includes several other 

 species under Schizoporella, but I am by no means sure that all 

 his species will remain in the same genus, for in (2) ^S*. unicorrds 

 Johnst. and var. errata Waters, *S'. longirostris Hincks, S. spon- 

 gites, /S. biaperta Mich., the sinus is much narrower, and what is 

 of most importance, the muscular attachments are some distance 

 from the border of the operculum. In S. hiaperta the ovicell 

 has a flat area with perforations round the border. 



(3) In the group *S'. vulgaris Moll., S. viridis Thorn., there is a 

 similar operculum, and it is in part the Escharina of Levinsen. 



In the same place I showed that there was a group which 

 might be placed in a modified Bioffonella Jullien, in which the 

 surface of both the zoarium and the ovicell is imperforate, also 

 there is a small suboral avicularium, and the opercula have the 

 muscular attachments some distance from the border as in the 

 last group. It is represented by aS'. ridleyi MacG., S. simplex 



I consider that the chitinous operculum was under the closure, and I should like to 

 see the name operculum confined to the movable chitinous appendage. Levinsen 

 on Plate i. figs. 15, 16, shows Meliceritites vielhanci d'Orb. with tubules to the 

 closures, such as 1 have seen in recent Cheilostomata, and a number of similar 

 closures are figured. Without there being perhaps any wide divergence of view I 

 should not describe these as being regenerated zooecia, for while Levinsen has de- 

 scribed regenerated zooecia, I have not seen an3'thing to suggest their being common, 

 and further, although we know that the polypides are regenerated in the closured 

 zooecia. this bj^ no means always takes place, as, for example, in the older parts of 

 stems and when there is more than one layer. It thei-efore seems unadvisable to 

 speak of them as regenerated zooecia when they are frequentlj- permanently closed. 



I have suggested to Professor Levinsen that the sunk walls with few openings as in 

 Meliceritites magnijica {op.cit. PI. i fig. 7), may be comparable with the perforated 

 wall or closure UffDEE the opeeculum in Vittaticella (see page 484). These are 

 also to be compared with the partial closure I described in M. roi/ana Waters, 

 Ann. Masr. Nat. Hist. ser. 6, vol. viii. pi. vi. figs. 2, 6 (1891). Levinsen in his most 

 valuable work has given full figures and descriptions of the structure of Melicerititidas, 

 and as I believe that many analogous structures are found in the Cheilostomata, a 

 thorough examination of the closures of living forms is much to be desired. 



* Waters, Report on Sudanese Bryozoa, p. 254. 



t Waters, Resultats du Voyage du S.Y. Belgica, " Bryozoa," p. 42 (1904). 



