118 PROCEEDINGS OF THE ACADEMY OF [Feb., 



their affinities with the central types of both species are so nearly 

 balanced that it is not really a matter of much consequence on which 

 side of them the imaginary boundary line of the species is drawn. . . . 

 It should be observed that the boundaries of the circles do not repre- 

 sent any facts which have an objective existence. With the boundary 

 lines we represent the species as described in books; without them 

 we see the species as they exist in nature." 



" Since the sub-types of species are distributed with great regard 

 to locality, it is obvious that much perplexity which results from the 

 graduation of species into each other is avoided by those travellers 

 who take but a few specimens from distant localities and by those 

 collectors who are satisfied with a single, well-characterized specimen 

 of each species. Such collections are valuable as exhibiting types, 

 but they very imperfectly represent the relations of types." When 

 we consider that Adams wrote these articles almost a decade before 

 the publication of the Origin of Species, we must be struck by the 

 modern view of a species which he takes. It was forced on him by 

 the great variability exhibited in the land snails of Jamaica, which 

 he was studying. In the foregoing paragraphs he lays down the 

 general principles of their variation as he saw it and points out the 

 necessity of collecting large series of specimens if we would become 

 acquainted with the relations of the forms to each other. Thus he 

 says that each species occupies one geographical area, and, as he found 

 in this island, these areas may be small. If we only compare selected 

 types from isolated areas the differentiation of the species is easy; 

 but when we disregard the artificial limits we set for one species and 

 examine not selected specimens, but large series, " we see the species as 

 they exist in nature." They vary from station to station, from one 

 set of conditions to another. Tracing the same species from one place 

 to another or finding it living under different environments, the 

 variations represented by the dots on his hypothetical diagram grade 

 one into another and, as he points out, we see that " our circles (which 

 include the species) do not represent any facts which have an objective 

 existence;" in other words, our species are purely subjective. The 

 case is perhaps not quite as bad as might be judged from the above, 

 for the examination of a large series of specimens from a single locality 

 may show all grades of variation between the central type and the 

 surrounding forms; or, on the other hand, it may show a remarkable 

 uniformity in the entire series, with only variations in the dimensions. 

 Thus, in one subspecies considered in this paper, forms from a single 

 locality could be selected, which, if reported from different zoological 



