526 Notices of Books. [October, 



which, with many changes of condition produced by the same 

 oscillations which alternately exposed and submerged the ter- 

 tiaries, existed continuously, depositing conformable beds of 

 chalk-mud from the period of the ancient chalk." 



The important bearing of these conclusions upon the very 

 foundations of geology are obvious enough, and are rendered 

 more strikingly so when expressed in the still more pointed 

 language of Professor Huxley, "that the modern chalk is not 

 only the lineal descendant, so to speak, of the ancient chalk, but 

 that it remains, so to speak, in possession of the ancestral 

 estate ; and that from the cretaceous period (if not much earlier) 

 to the present day the deep sea has covered a large part of what 

 is now the area of the Atlantic. But if Globigerina and Tere- 

 bratula, caput serpentis and Beryx, not to mention other forms of 

 animals and plants, thus bridge over the interval between the 

 present and the mezozoic periods, is it possible that the majority 

 of other living things underwent a sea-change into something- 

 new and strange all at once ? " 



Such suggestions are almost revolutionary, and if confirmed 

 they will cruelly spoil the orthodox lecture-room diagrams of the 

 geological ladder and the common stratigraphical descriptions of 

 superposition of rocks in the order of time. All the symmetry 

 of geological chronology will be destroyed if the cretaceous 

 system is to run up through the eocene, the miocene, the pliocene, 

 the pleistocene, and the recent ; and we must cease to call these 

 by the name of " periods," as they may merely indicate localities 

 or variations of sea-depth. If the chronological conclusions 

 based upon the stratigraphical arrangement of these later rocks 

 are thus shaken, may not something analogous have occurred 

 when the lower rocks were forming ? May there not be other 

 cases where depths of ocean have been mistaken for depths of 

 time ? or, in other words, may not many geological formations 

 hitherto described as deposited successively have actually been 

 proceeding, to some extent, simultaneously ? 



Thus, again, we are presented with an important phase of the 

 great question of evolution. If the creatures now living in the 

 great depths of the Atlantic can be proved to be the true 

 descendants of those of our chalk cliffs, and their line of an- 

 cestry can be traced continuously, we have command of a vast 

 period of time under which to study the laws of modification of 

 varieties, of species, and even perhaps of genera. 



But these are problems of vast magnitude, which the cruises 

 of the Lightning and the Porcupine have only opened or sug- 

 gested, and which we may hope that the Challenger will open 

 yet wider ; their complete solution will demand an amount of 

 further research proportionate to their magnitude and great phi- 

 losophical importance. 



We are satisfied that every reader of " The Depths of the 

 Sea " who is earnestly interested in the progress of Science and 



