6 ANNALS NEW YORK ACADEMY OF SCIENCES 



such a way that a very delicate, blind and legless lizard AYOuld be enabled 

 to reach a suitable environment on shore. I only ask the reader to tramp 

 "West Indian shores Avith this in mind. If a pair or a gravid female did 

 not make the voyage the process would have to be repeated promptly. 

 Now consider the number of rafts each of which Avould have to carry an 

 amphibian or a pair of them and which would have to start on their 

 journeys before one would reach shore so as to permit a landing such as 

 I have indicated Think of the number broken up at sea, and the still 

 greater number broken up on a tropic beach — where the sun would in- 

 stantly kill crawling amphisbsenians — and we see at once how excessively 

 improbable is a single occurrence such as this. But the important point 

 is that five West Indian Islands support ]oeculiar amphisbsenians ; two 

 species occur upon Cuba, two others related to these two on Haiti and 

 two others similarly related to the Haitian types on Porto Eico, while 

 but one type is as yet known upon St. Thomas and Sta. Cruz. To ac- 

 count for the presence of these creatures, then, eight practically incon- 

 ceivable voyages must be postulated, and I have only cited one improb- 

 ability out of many hundred necessary to derive all the organisms prac- 

 tically or wholly incapable of such sea travel and which are found in the 

 Greater Antilles. A few such cases as Amphisbsena settle the status of 

 the greater Antillean fauna to my mind absolutely, paucity of mammals 

 and possibly disputable geologic evidence to the contrary notwithstanding. 



Matthew's second premise is: "2) The time of such observation of 

 rafts covers about three centuries (I set aside the period of rare and oc- 

 casional exploring voyages). The duration of Cenozoic time may be 

 assumed at three million years (Walcott's estimate)." But is it not true 

 that this multiplication of time or any other, of course, affects only the 

 number of rafts and does not in any way alter the resistance to raft con- 

 ditions of the creatures which I have already chosen above as examples 

 or the possibility of their being able to swim. It really carries no weight 

 in this connection. 



Matthew's third point: "3) Living mammals have been occasionally 

 observed in such records of natural rafts. Assume the chance of their 

 occurrence (much greater than of their presence being noted) at one in 

 a hundred." We readily agree to the assumption and know that during 

 the few years of human observation rafting mammals have been observed. 

 It occurs to U.S, however, that multiplying the three hundred years' time 

 of human voyages by the ten thousand necessary to occupy even the short 

 Cenozoic period and then with this condition met, we find mammals 

 infinitely rarer upon all islands than they should be if rafted according 

 to Matthew's postulate. Similarly we find many of the reptiles most 



