26 Coelenterata. 



between the different Chagos banks and to the probability that considerable 

 current is felt even at 500 fms. The reefs of Chagos are in no way peculiar 

 except in their paucity of animal life, but this is amply compensated by the great 

 quantity of nullipores which practically form the outgrowing seaward edges of 

 the reef. Were it not for the abundance of nullipores there would be no atolls 

 with surface reefs in the Chagos. The lagoon shoals of Egmont are covered 

 by them and alone reach the surface, having done so they die and become 

 hollowed out in the centre finally resembling miniature atolls. The bottom of 

 the lagoons of the Chagos are bare rock, hard sand or mud with shoals aris- 

 ing precipitously here and there built up by a few species of coral, but largely 

 covered by Xenia and Sarcophytum, as are also the only two submerged banks 

 (Wight and Centurion) examined. Diego Garcia lagoon is almost completely 

 surrounded by land. Everywhere the land is entirely of coral origin. Diego 

 Garcia shows signs of a recent elevation of a few feet but there is very little 

 change since the survey of 1837, and the author believes that the present con- 

 dition of its reefs is mainly due to agencies still in action. The soundings 

 show that there is but a slender basis of support for any hypothesis as to the 

 possible former connection of the Maldive and Chagos Banks. Farquhar Atoll 

 shows no trace of elevation and has not been formed, as has been stated, by 

 submarine deposits. There is no close connection between this atoll and Mada- 

 gascar nor between the former and the Seychelles. The Mauritius reefs vary 

 from fringing to barrier, they slope gradually to 40 fms., succeeded by a steep 

 to 150 fms. then gradually falling in five miles to 1000 fms. 



Yoshiwara concludes that the raised reefs of the Riukiu Curve are mostly 

 later than the Tertiary period and are overlaid by recent rocks. They are 

 horizontal and either covered the sea bottom or fringed the margins of islands. 

 The northern limit of the ancient reefs in the western Pacific is 29 N. 

 The maximum elevation of the raised reefs of the Riukiu Curve is 684 feet, 

 they are distinguished from recent reefs by their position, structure and colour, 

 and are often found in the shape of terraces. The reefs are similar to those 

 now growing in the same region and have been upheaved after a gradual 

 depression. - - See also Grabau and Voeltzkow. 



B. Alcyonaria. 



See Hickson('), Roule, Simpson( 2 ), Thomson! 1 ), Thomson & Henderson ( 2 ), 

 supra p 25 Gardiner( 2 , 3 ) and p 25 Branner; for fossil forms see Capeder, 

 Drevermann, Etheridge(V), Gu'rich. 



Hickson( 2 ) recorded from about 60 miles off Achill Island (West of Ireland) 

 Pleurocorallium johnsoni(382 fms.), Cirripathes 1, Antipathella 1, Stichopathes 1 

 and also Ceratoisis, Stachyodes and Eunephthya, all these being new to the 

 British fauna. 



Hickson( 3 ) finds that in Melitodes the colour and size of the spicules and 

 the length of the internodes, characters often regarded as of specific value, 

 vary to such an extent that he places all the specimens from the Maldives in 

 one species, M. variabilis n. He also describes Aoanthogorgia 1 n., Bebryce sp,, 

 Acamptogorgia 1 n., Elasmogorgia 1 n., Muricella 1, Ads sp. ?, Gorgonella 1, 

 Juncella 3 (a brief revision of this genus is given and Ellisella is merged with 

 it), Scirpearia 1 n. sp., 1 var., Scirpearella 1 n., Pennatula 1, Eunephthya 1 n. 



According to Hill the egg of Alcyonium digitatum produces no polar bodies 

 in the ordinary sense of the term, but before the entrance of the spermatozoon 

 the female pronucleus undergoes irregular and amitotic division, the process 



