( Iv ) 



Keys ; that is, the Keys lying between this island and Grenada 

 has a fauna different from either, and, as I stated in my last 

 letter, much more closely related to the fauna of Demerara. 

 If you can explain this, I cannot. I might suppose thatthe Keys 

 have been submerged, and subsequently repeopled, like volcanic 

 islands, but, if so, why should the emigrants strilie the Keys, 

 and not St. Vincent or Grenada ? It is true that a depression 

 of 1600 ft. would cover all the Keys, while leaving St. Vincent 

 and Grenada above water, but I am averse to such forced 

 theories, unsupported by other evidence : besides, the barrier 

 reefs and other features point to a depression still going on. 

 Perhaps larger collections from Grenada will throw more light 

 on this knotty point. A few spiders which a friend sent me 

 from Barbadoes do not help the question, as they are all wide- 

 spread species found here and in the Keys. The spiders seem 

 to me particularly well adapted for studying problems of 

 geographical distribution ; for while a few kinds living in 

 houses or along the sea-coast have become widely distributed, 

 the majority do not readily cross water-barriers ; I noticed 

 this in the Amazons, where the river separated very many 

 species. I am glad, for this reason, that my spider-collection 

 from this island is so large ; it will form an excellent basis of 

 comparison with other islands. But for such studies, very 

 thorough collections are necessary, else mistakes may be 

 made. I noticed an instance to the point. Fronting the bay 

 before this village there is a small island, at one point 

 separated from the main island by a passage not more than 

 seventy yards wide, and with a rock above tide-level in the 

 middle. On this island I have on one or two occasions 

 obtained a spider belonging to a genus found in Brazil and 

 Mexico, but which I have not seen elsewhere on St. Vincent. 

 It is, of course, possible that the species is confined to this 

 little island, but it is extremely improbable. Found on one 

 of the Keys, I might have taken this spider as an instance of 

 the separation of the Keys zoologically from St. Vincent and 

 their relation to S. America. 



" By the way, though your St. Vincent collection will not be 

 strong, it will, beyond doubt, be the most thorough one in 

 Entomology ever made at one point in the tropics. And 



