390 



Plate X. 



Fig. 1 a. Retepora Beaniana King, on Hydroides norv'e- 

 gica. The colony, of which the uppermost 

 part is removed, is attached by a large plate- 

 like expansion, formed by kenozooecia, and 

 the external surface of the colony is like- 

 wise formed by a kenozooecial layer. X 12. 



— lb. The same species. Ooecia in different devel- 



opmental stages. X 40. 



— 1 c. A developing colony of the same species, 



consisting of one ancestrula, two fully devel- 

 oped zooecla and two developing zooecia. 

 X 40. 



— 1 d. A somewhat older colony of the same spe- 



cies, in which a root-expansion of kenozooe- 

 cia is already formed. X 17. 



— 1 f. A young colony of the same species, viewed 



from above. X 12. 



— 1 g. A portion of a root-expansion (from the 



colony in 1 d) more highly enlarged. The 

 distal walls furnished with a uniporous 

 rosette-plate are seen between the youngest 

 developing kenozooecia and the kenozooecia 

 on the inner side. X 40. 



— 1 h. A portion of the same expansion. A finished 



kenozoOECium with avicularium is seen, and 

 besides, four developing kenozooecia, which, 

 like those shown in fig. 1 a, have had a 

 membranous cover, which has disappeared 

 after boiling in potash. X 40. 



— 2 a. Retepora cellulosa Smitt. The proximal part 



of an old colony cut across transversally. 

 The superficial kenozooecial layer is seen. 

 X 12. 



— 2 b. The same piece as shown in fig. 2 a, but the 



transversally cut surface is seen. The three 

 groups (2, 4, 6) of small round apertures, 

 almost in the centre of the section, are 

 intersected zooecial chambers, which on both 

 sides are covered by kenozooecia (see page 

 293). X 12. 



Fig. 2 c. A transverse section through a much young- 

 ger portion of the same colony. The zooecia 

 are also here on both sides covered by keno- 

 zooecia. X 12. 



— 2 d. A part of the transverse section in flg. 2 b, 



more highly magnified. The separating walls 

 furnished with uniporous rosette-plates are 

 seen betwen the kenozooecia placed above 

 each other. X 40. 



— 2 e. Another part of the same transverse section, 



in which the cavity of the kenozooecia is 

 much narrower. X 40. 



— 3 a. Retepora Wallichiana, Busk. Stalked ooecia. 



X 40. 



— 3 b. A transverse section through a branch of 



the same. Three zooecia and two kenozooecia 

 are cut throngh. X 40. 



— 4 a. A transverse section through a branch of 



Retepora tesselata Hincks. The small holes 

 are transverse sections of kenozooecia. X 23. 



— 4 b. A transverse section through a younger por- 



tion of a colony of the same species. A layer 

 of zooecia and a layer of kenozooecia are 

 seen; in some of the former the uniporous 

 rosette-plate of the distal wall is seen. X 23. 



— 4 c. A transverse section through a colony of 



the same species with two layers of zooecia. 

 X 23. 



— 4 d. The same species. A portion of the keno- 



zooecial layer. X 17. 



— 5 a. A transverse section through a colony of 



Retepora lata Hincks. The small holes are 

 from kenozooecia. X 23. 



— 5 b. The same species. The zooecial layer, from 

 * the basal surface, after detachment of the 



kenozooecial layer. — 23. 



— 5 c. The same species. A part of a kcnozooecium 



with avicularia from which pore-canals issue 

 to the surface. A covered avicularium is 

 visible in the distal part. X 55. 



