POPULAR MISCELLANY. 



139 



recognizing different marine deposits as of 

 like age from their organic remains, terres- 

 trial and fresh- water beds would in all proba- 

 bility be referred to widely differing epochs, 

 and that some would be more probably 

 classed with a past period than with others 

 of the present time. The idea that marine 

 and terrestrial faunas and floras were simi- 

 lar throughout the world's surface in past 

 times is so ingrained in paleontological sci- 

 ence that it will require many years yet for 

 the fallacy of the assumption to be gener- 

 ally admitted. No circumstance has con- 

 tributed more widely to the belief than the 

 supposed universal diffusion of the carbonif- 

 erous flora. The evidence that the plants 

 which prevailed in the coal-measures of 

 Europe were replaced by totally different 

 forms in Australia, despite the closest simi- 

 larity between the marine inhabitants of 

 the two areas, should go far to dispose of 

 this belief. Hence, determinations of the 

 age of terrestrial beds based upon their fos- 

 sil faunas and floras should not be accepted 

 as fixed unless they are accompanied by 

 evidence from marine beds. 



Discussing the " Physiology of Deep-Sea 

 Life " in the Eiological Section, Profess- 

 or Moseley, of the Challenger Expedition, 

 having recognized the value of the work 

 that had been done in deep-sea investiga- 

 tion in the United States, spoke of the im- 

 portance to the physiologist of a knowledge 

 of the conditions under which gases occur 

 in a state of absorption in thQ ocean-waters. 

 Professor Dittmar's researches show that 

 the presence of free carbonic acid in ocean- 

 waters is an exception. Hence, the solution 

 which some shells undergo at certain depths 

 is probably due, not to the presence of free 

 acid, but to the solvent action of the sea- 

 water itself. Oxygen is present in all sea- 

 water, being derived from the surface, but 

 the amount diminishes, on account of the 

 oxidizing that is always going on, with in- 

 crease of depth. M. Regnaud's experiments 

 on the effects on organisms of high press- 

 ures, corresponding with those of certain 

 sea depths, show that a fish without a 

 swimming-bladder, or one with the bladder 

 emptied of air, may be subjected to a press- 

 ure of 100 atmospheres, or 650 fathoms, 

 without injurious effect; at 200 atmos- 



pheres, or 1,300 fathoms, it becomes torpid, 

 but soon revives when the pressure is re- 

 moved ; while at 300 atmospheres, or about 

 2,000 fathoms, the fish dies. The results 

 of these experiments would probably have 

 been greatly modified, if plenty of time 

 could have been given for the fish to ac- 

 commodate itself to the change of pressures 

 and the conditions in which it moves slowly 

 from one depth to another be imitated. M. 

 Paul Bert's experiments upon the effect on 

 aquatic organisms of water subjected to the 

 pressure of compressed air — a very differ- 

 ent condition — show fatal results at fifteen 

 and even at seven atmospheres. ' A large 

 proportion of the food-supply of the deep- 

 sea animals appears to be derived from life 

 on the ocean - surf ace, or that which is 

 brought to the surface by rivers from the 

 land sinking dovni to it. Deep-sea life ap- 

 pears to diminish in abundance as the coasts 

 are receded from. More may be known on 

 this subject when we have learned more 

 about pelagic vegetable life, with which our 

 acquaintance is now imperfect. If it shall be 

 ascertained that the deep sea derived its main 

 supply from the coasts and land-surfaces in 

 the early periods, there can have existed 

 scarcely any deep-sea f aima until the littoral 

 and terrestrial rfaunas and floras had be- 

 come well established. It still appears im- 

 possible to determine any successive zones 

 of depth in the deep-sea regions, character- 

 ized by the presence of special groups of 

 animals. Some groups seem to be charac- 

 teristic of water of considerable depth, but 

 representatives of them struggle up into 

 much shallower regions. This fact places 

 a difficulty in the way of determining the 

 depths at which the geological deposits 

 were formed. Something may be learned 

 of the depths of modern deposits by the ex- 

 amination of their microscopical composi- 

 tion and the condition of the shells and 

 spicules. Great uncertainty prevails as to 

 whether, or to what extent, the intermedi- 

 ate waters, which are held to include about 

 eight ninths cf the bulk of the entire ocean, 

 are inhabited by animals. A feature of the 

 deep-sea fauna is the general absence from 

 it — except as to mollusks and brachiopods — 

 of palEeozoic forms. This fauna has, doubt- 

 less, been derived almost entirely from the lit- 

 toral fauna, which also must have preceded, 



