3o8 DEPTHS OF THE OCEAN 



Lauder. the shorcs of England, by Lauder at Hong-Kong, and by Cleve 



cieve. in the North Polar Sea and at Java. A regular gold mine in the 



Waiiich. way of rare pelagic forms was found by Wallich in the intestinal 



canals of salpse, and this source has subsequently been utilised 



for procuring forms that our apparatus could not capture. 



Pelagic algae which have no skeletons of durable mineral 



constituents, such as silicic acid or lime, were in those days 



neglected. A few, no doubt, of the larger peridinese were 



Nitsch. described by Nitsch, Ehrenberg, Bailey, Claparede, and 



ciaparede. Lachmaun ; but there was very little progress made, and it 



Lachmann. ^as uot till 1 883 that T. R. von Stein published his first 



Stein. comprehensive monograph, a great deal of the material for 



Bergh. which had been taken from the stomachs of salpse. R. S. Bergh 



had already issued, two years previously, a text- book on the 



organisation of these algse. 



Since 1870 important expeditions have been undertaken, 

 one object of which was to study the pelagic organisms 

 " chaiiengei •' systematically. The "Challenger" Expedition, in particular, 

 Expedition. collected quantities of material from all the seas of the world ; 

 though attention was still chiefly directed to those forms whose 

 coverings are met with in deposits on the sea-bottom, that is to 

 say, diatoms with their silicious coverings, and the remarkable 

 little organisms forming the microscopic calcareous bodies which 

 Ehrenberg had already designated coccoliths and rhabdoliths. 

 John Murray. Murray pointed out that coccospheres and rhabdospheres, as 

 they were termed, are really self-existent organisms in the 

 surface-layers. He could obtain them by allowing a glass of 

 sea-water to stand for a few hours, so that they sank to the 

 bottom and attached themselves to threads placed there for 

 purposes of experiment ; and he also found numbers of them in 

 the stomach-contents of salpse, of which they often formed an 

 essential part. It was possible, too, by noting the occurrence 

 of their coverings in the bottom-samples, to obtain definite 

 information regarding their geographical distribution. He 

 observed that, while they are abundant in all tropical and sub- 

 tropical waters in the open ocean, they are not found in arctic 

 and antarctic waters having a temperature below 45° F., nor are 

 they to be found in the deposits of the polar oceans. Murray 

 further ascertained that diatoms are irregular in their occurrence, 

 and that they are more numerous in coastal areas than out in 

 Castracane. the oceau. Unfortunately Castracane, when examining the 

 diatoms collected by the expedition, was unable to find any 

 conformity in the distribution of the different species. 



