THE FIRST ALBATROSS EXPEDITION 267 



region, but the speculations are all based upon data 

 supplied by collections made upon the littoral regions. 

 It was not until the collections made by the Blake on 

 the Atlantic and Caribbean side, and by the Albatross 

 on the Panamic side, were studied, collections extending 

 to the deepest waters of both regions, that we were able 

 to speculate with some degree of certainty upon the 

 causes which led to the existence of the peculiar fauna 

 characteristic of the deep waters of the Caribbean, a 

 fauna more closely allied to the Panamic deep-water 

 fauna than to that of the Atlantic, and suggesting that 

 after the formation of the Windward Islands, which, in 

 great part, cut off the Caribbean from the Atlantic, there 

 must have been a free connection with the Panamic 

 region of a depth greater than that which connected it 

 with the Atlantic. 



" It of course became necessary to carry on geological 

 surveys to determine the age at which these connections 

 were established, and again closed, to obtain some meas- 

 ure of the time elapsed necessary to differentiate the 

 marine fauna of the two sides of the Isthmus of Panama. 

 While the length of this period can only be vaguely 

 inferred, it gives us at any rate the comparative measure 

 of the changes which have taken place in these faunae 

 from the time when the marine fauna of the later Cre- 

 taceous was passing into the older and more recent 

 Tertiaries, and until the existing state of things was 

 established. The preliminary geological studies I car- 

 ried on in connection with the study of the West In- 

 dian coral reefs, necessary to determine the age of the 

 development of the larger Antilles and of the Wind- 

 ward Islands, have been extended for me by Hill and 

 others, so that we now have a fair idea of the geolog- 



