11)22] Biological Studies in Madeira 561 



WEEKLY EVENING MEETING. 



Friday, May 5, 1922. 



Sir James Reid, Bart., G.C.V.O. K.C.B. M.D. LL.D., 

 Manager and Vice-President, in the Chair. 



Michael Grabhau, M.D. F.R.C.P. 



Biological Studies in Madeira. 



Though a mere speck on a map of ordinary size, the group of 

 mountain tops comprising the archipelago of Madeira really occupies 

 a considerable oceanic area ; for the two main islands are quite 

 twenty-five miles apart, and the various rocks in the district are 

 separated by many miles of latitude and longitude. 



Each island and each considerable rock has been almost certainly 

 a distinct focus of volcanic ejection arising individually from the 

 abysmal oceanic floor ; each has its own loneliness and structure, and 

 all the evidence is adverse to the theory that there was once another 

 Atlantic continent of which these deeply-weathered and highly- 

 sculptured hills and rifts survive from early Tertiary times. The 

 suddenness with which each rocky shore passes beyond the hundred- 

 fathom line into the profound Atlantic depth below is conclusive as 

 to the distinct origin of each portion of the group. 



The biological conditions, moreover, distinctly confirm the 

 geological evidence in this respect ; for taking the Testacea alone, of 

 which the Madeira archipelago possesses quite 170 distinct examples, 

 each island, each rock has its own peculiar examples ; and of the total 

 number of these pulmoniferous species, six or seven only are common 

 to all the islands of the group. They have lived in segregation since the 

 various and varying agencies of transport first brought them hither 

 over the sea, and you may find them recent and with their cognate 

 sub-fossilized ancestry now as w T hen in past ages they were first and 

 separately deposited on the profoundly separated land surfaces of the 

 district. You might lower the Atlantic level a hundred fathoms 

 without merging the component rocks of the archipelago in a 

 common connection, and the evidence of the pulmoniferous gastero- 

 pods is at once copious and conclusive as to their separate volcanic 

 origin. 



The conditions around us here, in the British islands, are entirely 

 different ; for though the Scilly islands are as far from Cornwall as 

 the northern Madeiran island Porto Santo from Madeira, the con- 

 chologist obtains no distinct species or even marked races in these 



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