' Travailleur ' Zoological Exploration. 41 



Beyond 600 metres and down to 2660 metres they were 

 represented only by Tetillce and Holtenia Carpenteri. The 

 latter species approaches much nearer the surface in the 

 Mediterranean than in the Atlantic ; we have ascertained its 

 existence at 307 metres off Toulon ; and in this zone it occurs 

 with certain representatives of the littoral fauna, such as 

 Polymastia mamillaris and Tethya lyncurium. 



It results from our investigations that the Mediterranean 

 must not be regarded as forming a distinct zoological province ; 

 we believe that this inland sea has been populated by the 

 immigration of animals coming from the ocean. These, 

 finding in this recently-opened basin * a medium favourable 

 to their existence, established themselves in it definitively ; 

 and often their development and reproduction have taken 

 place more actively than in their original locality. Near the 

 shores especially the fauna exhibits a luxuriance which the 

 other European coasts rarely present. One can easily under- 

 stand that some of these animals, placed under novel biological 

 conditions, have become slightly modified in size or in other 

 external characters, which explains the slight differences 

 existing between certain oceanic forms and the corresponding 

 Mediterranean forms. If the primordial separation of the 

 two faunas has been accepted, this is because the productions 

 of the Mediterranean were compared with those of the North 

 Sea, the English Channel, or the coasts of Brittany, whilst 

 those of Portugal, Spain, Morocco, and Senegal ought to have 

 been selected as terms of comparison. The animals of these 

 regions must, in fact, have been the first to emigrate towards 

 the Mediterranean ; and in proportion as we know these faunas 

 better, we see the differences which zoologists thought they 

 could observe between them gradually disappear. 



The explorations that we had made in the Mediterranean 

 during the month of July necessitated some complementary 

 researches in the Atlantic, especially on the coasts of Spain 

 and Portugal ; and the Minister of Marine authorized us to 

 continue our dredgings on board the ' Travailleur ' during 

 the month of August. 



In the abyssal parts of the Atlantic, the bottom, instead of 

 being uniformly covered by a thick bed of ooze, was of a very 

 varied nature, and formed sometimes of compact limestone, 

 sometimes of pebbles resembling Pyrenean rocks in their 



* See, as to the period of tlie formation of tlie Mediterranean, Blan- 

 cbard, " La Geographic enseig-nee par la nature vivaute " (Bull. Assoc. 

 Sci. France, July 7, 1878, p. 200). 



