166 ENDEMISM AND DISTRIBUTION: SPECIES [pt. ii 



area, being distributed upon exactly similar principles, and like 

 them showing many of small area, with numbers diminishing at 

 first rapidly, and then more slowly, towards the few that occupy 

 large areas, the effect of the figures, when plotted graphically, 

 being to form a hollow curve (fig. on p. 162). 



One may almost regard the question of endemism as the central 

 point of taxonomic distribution, upon which all the rest depends. 

 Controversy has largely centred around it, and there are at least 

 three rival explanations in the field at the present time. These 

 are (1) that endemics are very specialised species (and genera) 

 suited only to the areas upon which they are found; (2) that 

 they are old species (and genera) which have been driven into 

 quiet nooks, or left in odd corners, by the competition of better 

 adapted species; and (3) the explanation just given, that in 

 general they are young beginners, descended from the "wides." 



The first and second explanations were based upon incom- 

 plete knowledge of the distribution of endemics, and can no 

 longer be regarded as general. One has only to think over what 

 has been pointed out above (and cf. p. 55). The facts (1) that 

 the endemics are distributed in "wheels within wheels" (cf. 

 maps given above), (2) that the numbers in any genus in a 

 country increase from the edge up to a maximum at some point 

 or region, (3) that this is the same place at which many other 

 genera have also their maxima, (4) that there may be more than 

 one place in a single country (p. 78) where these maxima aggre- 

 gate together, (5) that the distribution of the endemics by areas 

 forms hollow curves, increasing most rapidly to the smallest 

 areas of all, (6) that these hollow^ c\irves show for country by 

 country, for family by family, e^en for genus by genus, (7) that 

 there is no difference in type of distribution between the species 

 of endemic genera, those of Avidely distributed genera with all 

 species endemic, and those of widely distributed genera with 

 some species endemic and some not, (8) that the species of 

 endemic genera show less dispersal in a country than the endemic 

 species of non-endemic genera, (9) that the endemic species 

 mainly belong, not to the endemic genera, or to small and broken 

 genera, but to the large, widely distributed, and "successful" 

 genera of the Avorld, (10) that endemic species are distributed, 

 and behave, just like other species, (11) that endemics increase 

 in numbers and proportion towards the south; to say nothing 

 of other facts already brought up, or of the difficulties in explain- 

 ing in any single case what characters are disadvantageous (as 



