84 EXPEDITION OF THE " CHALLENGER " m 



kind of rock, whicli Avas first pointed out by 

 Ehrenberg,^ is now admitted on all bands ; nor 

 can it be reasonably doubted, that ordinary meta- 

 morphic agencies are competent to convert the 

 " modern chalk " into hard limestone or even into 

 crystalline marble. 



Ehrenberg appears to have taken it for granted 

 that the' Glohigcrince and other Fcraminifcra which 

 are found in the deep-sea mud, live at the gi'eat 

 depths in which their remains are found ; and he 

 supports this opinion by producing evidence that 

 the soft parts of these organisms are preserved, 

 and may be demonstrated by removing the cal- 

 careous matter with dilute acids. In 1857, the 



^ The following passages in Elirenberg's memoir ob The 

 Organis'ms in the Chalk which are still living (1839), are con- 

 clusive : — 



* ' 7. The dawning period of the existing living organic creation, 

 if such a period is distinguishable (which is doubtful), can only 

 be supposed to have existed on the other side of, and below, the 

 chalk formation ; and thus, either the chalk, with its wide- 

 spread and thick beds, must enter into the series of newer 

 formations ; or some of the accepted four great geological periods, 

 the quaternary, teitiary, and secondary formations, contain 

 organisms which still live. It is more probable, in the propor- 

 tion of 3 to 1, that the transition or primary period is not 

 different, but that it is only more difficult to examine and 

 understand, by reason of the gradual and prolonged chemical 

 decomposition and metamorphosis of many of its organic 

 constitttents." 



"10. By the mass-forming Infusoria and Polythalamia, 

 secondary are not distinguishable from tertiary formations ; and, 

 from what has been said, it is possible that, at this very day, 

 rock masses are forming in the sea, and being raised by volcanic 

 agencies, the constitution of which, on the whole, is altogether 

 similar to that of the chalk. The chalk remains distinguishable 

 by its organic remains as a formation, btit not as a kind of 

 rock." 



