

upon the Distribution of the Fauna of the JEgean Sea. 173 



into account for the diminished number of identical species; 

 or more probably, this poverty of identical northern species 

 may arise from the peculiar condition of the sea-bottom at this 

 depth. Fuci having become rare in and below the sixth region 

 are replaced by occasional patches of Nullipora, upon which 

 the living Testacea in the lower regions are mostly found, pre- 

 senting prolific spots in the otherwise barren fields of yellow 

 clay, like an oasis in the desert. These peculiar conditions 

 develope necessarily a peculiar marine fauna, upon which the 

 climatal influence nevertheless stamps its characteristic form 

 throughout the species ; and, if identical forms are not known, 

 point to a far north clime for the locality in which they may 

 be found. 



The wide range in depth of the eighth region seems to be 

 in unison with its pervading temperature and more uniform 

 condition of the sea-bottom. 



Among the iEgean fauna there are several species which 

 have a considerable range in depth. Professor Forbes enu- 

 merates nine common to six regions, seventeen species to five 

 regions, and two which ramble throughout the eight regions. 

 " On inquiring into the history of the species," says the author 

 of the report, " which have such a wide range in depth, it is 

 found that more than one half are known to be wide geogra- 

 phic rangers ; and from these facts we may fairly draw a 

 general inference, that the extent of the range of a species in 

 depth corresponds with its geographic range." The obser- 

 vation I made on the cosmopolite species of the littoral tidal 

 zone, it will be remembered, is also equally applicable to these 

 wide rangers in depth ; for being adapted to climatal changes, 

 they consequently become wanderers over wide geographic 

 space, as they ramble into the representations of climate through 

 regions of depth. Thus we have the climate of a parallel re- 

 presented in marine depths as it is in terrestrial elevation. 



It will be seen by Professor Forbes's report, that the species 

 identical of a southern latitude are very few, these being con- 

 fined to the characteristic Mediterranean zone, or are wide 

 rangers. This is, consequently, in strict accordance with the 

 climatal influence. As a law resulting from this influence, 

 characteristic tropical and subtropical species will have a 

 limited distribution in geographic space; whilst the boreal and 

 sub-boreal characters will be found in every geographic posi- 

 tion where corresponding regions of depth are found with 

 animal life existing, the limit of which I believe to be much 

 lower than 300 fathoms, having examples from 390 fathoms. 

 But I must notice, that the iEgean deep dredges indicate ge- 

 nerally a zero of animal life at 300 fathoms, as Professor Forbes 



