222 NATURAL SCIENCE. April 



Then, towards the end of the Mesozoic period, cooling set in at 

 the neighbourhood of the poles, causing colder water, containing a 

 more abundant supply of oxygen, to flow into the deeper seas, which 

 were thereby rendered habitable. At the same time, the cooling of 

 the polar seas so changed the conditions that the fauna of the 

 shallow waters was impoverished and rendered sluggish, causing 

 evolution to take place there more slowly than in the tropics. It is thus 

 that Dr. Murray explains many of the main facts in the distribution 

 of polar marine life. The chapter of the memoir in which these 

 views are announced is full of original and most suggestive ideas. 



The theory of a gradually cooling globe has often been applied to 

 explain the puzzles of zoological distribution, but we still doubt its 

 value. When we turn to the list of ninety species which are common 

 to both the extra-tropical regions, we find so many are primitive 

 types — such as the eight sponges or the two echinoids, or are forms 

 which live attached to floating wood — such as two of the three lamelli- 

 branchs ; while, moreover, groups of which the range of species is 

 proverbially world-wide, such as the Ostracoda and Bryozoa, are so 

 largely represented (by eight and sixteen species respectively), that 

 we feel less convinced by the argument. Dr. Murray is perfectly 

 candid as to the fact that the occurrence of Palaeozoic glaciations 

 would have been fatal to his views. And no one who saw Professor 

 Edgworth David's series of photographic lantern slides of the Permo- 

 Carboniferous Glacial Deposits of Australia at a recent meeting of 

 the Geological Society can have any doubts as to the authenticity of 

 Palaeozoic glaciations. Professor David's demonstration shows that 

 we can expect no help from a gradually cooling globe in solving the 

 distribution of life, since at least Carboniferous time. 



Two Geographical Reconstructions. 

 The past and present distribution of European mammals, and 

 the light thrown thereby on the ancient geography of the Medi- 

 terranean district, are discussed by Dr. R. F. Scharff in a valuable paper 

 in the Memoires de la Societe Zoologique de la France (viii., pp. 436-474 ; 

 1895). Taking, in the first place, the living and extinct indi- 

 genous mammals of Ireland, the author shows that they all inhabited 

 Great Britain during the Forest Bed Period, while one at least — the 

 fox — was living here in the time of the Red Crag. The mammals 

 which are found — recent or fossil — in Great Britain, but not in Ireland, 

 began to arrive in our area at the time of the Forest Bed, and can be 

 traced through the Pleistocene deposits. These facts are used by 

 Dr. Scharff, with much force, in support of the view enunciated by him 

 in a previous paper {see Natural Science, vol. vi., pp. 147,148; March, 

 1895), tnat ^ e Irish fauna reached that island in Pliocene times. For if, 

 he argues, the prevalent view of a Pleistocene continental connection 

 be held, how is it that none of the animals of the second division were 

 able to reach Ireland ? 



