Spiders from the Bahama Islands. 323 



Should this paper fall into the hands of anyone interested 

 in the natural history of their surroundinf^.s, situated in any 

 of the islands of the Antilles, I would like to urge that 

 collections, however small, arc always valuable when brought 

 from adjacent islands forming a large group, more especially 

 if a number of examples of the commoner and more obvious 

 forms be sent also. 



In this way alone can we determine the identity of the 

 many forms which have been described from different islands 

 as distinct species ; and by securing sutficient material we 

 may be able to trace the gradual transition of a species 

 through successive islands until it passes into some extreme 

 form which has hitherto perhaps been regarded as a distinct 

 species. 



Given a sufficient lapse of time, each island may produce, 

 from the same original form common to the whole district 

 before its separation into groups of isolated islands, a species, 

 or at all events a local race, peculiar to itself, diverging under 

 different conditions, prevented by physical obstacles from 

 interbreeding with those of neighbouring islands, and thus at 

 last perhaps becoming a true species, physiologically distinct 

 as well as geographically separated; for in dealing with forms 

 in which the male and female are each highly specialized 

 individuals of different sexes the distinctness of two species 

 must depend on whether they will cross-breed or not normally, 

 as a rule, under natural conditions of life. If they interbreed 

 freely they cannot be distinct species, while if they interbreed 

 occasionally, but not as a general rule, the two forms may be 

 gradually becoming divergent, and finally become physio- 

 logically distinct. 



A variety is held to be an individual variation of either sex 

 where these sexes interbreed freely. A local race is composed 

 of individuals all of whose members diflfer slightly but con- 

 stantly from those of apparently the same species in another 

 locality more or less isolated from the first. The question as 

 to what is a species, a local race, and a variety is impossible 

 to settle definitely so long as the natural process of the sepa- 

 rating into groups and the elimination of intermediates is in 

 progress. 



Thus it is of very great interest to learn how far forms 

 which have probably been geographically separated for 

 centuries have passed through the stage of individual variation, 

 have reached the status of local races, or have already become 

 physiologically distinct Sj^ecies. 



The conditions for the observation of these phenomena 

 ought to be exceedingly favourable throughout the numerous 



