ON NEW AND RARE BRITISH SPlbERS. 5 



group of individuals sufficiently dfstinct to t bo characterised ' by 

 stated limits of form, structure, and probably colour, and thus 

 readily separable from that type of which at present we consider 

 the examples under consideration to be simply abnormal forms ; 

 in other words a new species would have been produced, and its 

 discoverer would be justified in so characterizing and describing 

 it. The formation of now species is a subject of great interest 

 as well as importance to Zoologists and Botanists. If the origin 

 of species by evolution, whether practically carried out by 

 natural selection or any other process (or as is most probable by 

 that and other methods) be a true position, species are undoubt- 

 edly still in course of formation. The groups of individuals in 

 which we should expect to find the process going on are those 

 called dominant ones; i. e. those which exceed others in the abun- 

 dance, in the wide distribution and in the liability to variation, of 

 their individual members, as also in their adaptability to very 

 varied circumstances and surroundings. Hence, in dealing with 

 such groups it is of great importance to obtain the longest possi- 

 ble series of individuals of both sexes from evorjkind of locality; 

 to form, in fact, a collection on exactly the opposite principle to 

 that on which some collectors of insects (notably, L"pidoptera,} 

 used to form their collections, that is by discarding every speci- 

 men of an acknowledged species which presented the least 

 variation from the normal type, on the score that such specimens 

 made the goodly rows in the cabinet look uneven and unsightly. 

 Among spiders one of these dominant groups is certainly that 

 which comprises Neriene atra, BL, N.longipalpis, Sund., and 

 some others, more or less closely allied, forming in fact the 

 restricted genus, Erigone (Sav.). Mr. J. H. Emerton, an American 

 Arachnologist, sent to me some years ago from North America 

 a largo number of spiders of this group indiscriminately col- 



> (! > . - . 



lected and all mixed together. After carefully examining every 

 individual I came to the conclusion that there were among them 

 several distinct forms, which I shortly afterwards described and 



v 1 <^ 



characterised as distinct species ; but still a number of examples 



