Cl THE VOYAGE OF H.M.S. CHALLENGER. 



investigations are forthcoming, indicate a very rich development of Radiolarian life. Pro- 

 bably it approaches more nearly the fauna of the Pacific than that of the Atlantic, both as 

 regards the abundance and the morphological characters of its species. The researches of 

 the Challenger are very limited and incomplete as regards the Indian Ocean, for the 

 expedition only just touched upon this great ocean basin (2000 to 3000 fathoms deep) at 

 its two extremities (westwards at the Cape of Good Hope and eastwards at Tasmania), 

 its course lying for the most part south of lat. 45 S. and extending beyond lat. 65 S. 

 (from Station 149 to 158, south of lat. 50 S.). It is true that this portion of the South 

 Indian Ocean was shown to contain Radiolaria everywhere, but these were more plentiful 

 in individuals than in species. Only from Station 156 to Station 159 (between lat. 62 

 and 47 S., and long. 95 and 130 E.) was the bottom, which consisted partly of Diatom 

 ooze and partly of Globigerina ooze, richer in species (see note A). The gaps left by the 

 Challenger in the investigation of the Indian Ocean, have, however, been to some extent 

 filled from other sources. As early as 1859 the English "Cyclops" expedition had 

 shown that the bottom of the Indian Ocean to the east of Zanzibar (lat. 9 37' S., 

 long. 61 33' W.) is covered with pure Radiolarian ooze (see note B). Also since the 

 Tertiary rocks of the Nicobar Islands are for the most part of the same composition, and 

 since a great abundance of Radiolaria has been shown to be present both in the east part 

 of the ocean, between the Cocos Islands and the Sunda Archipelago (see note C), and in 

 the northern part or Arabian Sea between Socotra and Ceylon (see note D) ; it may be 

 assumed with great probability that the greater part of the basin of the Indian Ocean, 

 like that of the Pacific, is covered either with Radiolarian ooze or with the characteristic 

 red clay. With this agrees the richness of the surface of the Indian Ocean in Radiolaria 

 of the most various groups, which has been more extensively demonstrated. 



A. The Eadiolarian fauna collected by the Challenger on the voyage from the Cape to Mel- 

 bourne, shows in part, namely, from Station 156 to Station 158, very peculiar and characteristic 

 composition ; in particular, the Diatom ooze of Station 157 passes over in great part into a Eadio- 

 larian ooze, mainly composed of Sphserellaria. This is worthy of a more thorough investigation 

 than I was able, owing to lack of material and time, to give it. 



B. The remarkably pure Eadiolarian ooze of Zanzibar, discovered by Ehrenberg in 1859, was the 

 earliest known recent example of that deposit. It was brought up by Captain Pullen of the 

 English man-of-war " Cyclops," from a depth of 2200 fathoms, between Zanzibar and the Seychelles, 

 and " under a magnifying power of 300 diameters, showed at the first glance a mass of almost pure 

 Polycystina, such as no sample of a deep-sea deposit has hitherto shown. It is very noticeable 

 that in the whole of this mass of living forms, no calcareous shells are to be seen " (Ehrenberg, 

 L. N. 24, pp. 148, 149). 



C. For the most important material from the Indian Ocean, I am indebted to Captain Heinrich 

 Eabbe of Bremen, who during many voyages in the Indian Ocean, in his ship " Joseph Haydn," 

 made numerous collections in different localities with the tow-net and the trawl, and admirably 

 preserved the rich collections thus made. The greatest abundance of Eadiolaria was found in those 



