XXX* PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



shall content myself with reminding you of some of the more import- 

 ant conclusions, as bearing on geological investigations, which are 

 embodied in it. The most important fact which has resulted from 

 them respecting the development and distribution of animal and 

 vegetable life in the depths of the ocean is, that of the almost uni- 

 form occurrence of particular species in particular zones of depth 

 below the surface. This distribution of marine animal life is deter- 

 mined by three primary, modified by several secondary influences. 

 The primary are climate, sea composition, and depth ; of the many 

 secondary influences, the most important is the character of the 

 sea bottom. According as rock, mud, sand, weedy or gravelly 

 ground prevails, so will the number of the several genera and species 

 vary. The outline and geological nature of the coast is also an im- 

 portant feature in modifying the marine fauna. Other secondary 

 influences are tides and currents, the influx of fresh water, &c. 



We have then a full description of eight well-marked regions of 

 depth in the Eastern Mediterranean, each characterized by its pecu- 

 liar fauna, and when there are plants by its flora. These regions 

 are distinguished from each other by the association of the species 

 they severally include. Certain species in each are found in no 

 other, several are found in one region which do not range into the 

 next above, whilst they extend to that below, or vice versa ; certain 

 species have their maximum of development in each zone, being most 

 prolific in individuals in that zone in which is their maximum, and 

 of which they may be regarded as especially characteristic. Every 

 zone has also a more or less general mineral character, the sea bottom 

 not being equally variable in each, and becoming more and more 

 uniform as we descend. Again, the deeper zones are greater in 

 extent, so that whilst the first or most superficial is but 12, the 

 eighth, or lowest, is above 700 feet in perpendicular range ; its hori- 

 zontal extent increases in a somewhat similar proportion. Another 

 significant feature is, that as we reach the eighth zone the number 

 of species and of individuals diminishes as we descend, pointing to a 

 zero in the distribution of animal life as yet unvisited. Species 

 disappear in depth which do not seem to be replaced by others. 

 From other observations the following general inference is deduced ; 

 that the extent of the range of a species in depth is correspondent 

 with its geographical distribution. 



But these eight regions are themselves the scene of incessant 

 change ; not only are the depths modified by the addition of fresh 

 matter, but the very animals themselves, by their own increase, so 

 modify the nature of the sea bottom as to render it unfit for their 

 own existence, until a new layer of sedimentary matter, uncharged 

 with living organic contents, has formed a fresh soil for similar or 

 other animals to thrive on. It is impossible to overlook the im- 

 portance of these observations in explaining many of the daily 

 recurring pheenomena which are brought under the notice of the 

 geologist ; in the last observation we may see an explanation of the 

 phsenomenon of interstratification of fossiliferous and non-fossiliierous 

 beds. 



