390 



OLIGOCHAETA 



difficult to understand, the perpetually frozen undersoil of the 

 Arctic regions. Eisen has described a number of species from 

 Spitzbergen, and Colonel Feilden recently sent me an example 

 of Allolobophora octoedra from Kolguiev, where Mr. Trevor-Battye 

 also saw another specimen. The family is characteristic of the 

 Nearctic and Palaearctic regions, and though found beyond them, 

 is probably elsewhere an accidental importation (see p. 371). 

 There are at least fifteen species of this family found in 

 England and Ireland, and probably more will be identified. 



There does not exist at present any comprehensive account of 

 the British species of earthworms, though all of them are 

 included in Dr. Rosa's recent revision of the family. Most of 

 the British forms belong to the genus Allolobophora, which may 

 be divided into two series according to whether the chaetae 

 are quite close together or further apart. The extent of the 

 clitellum and the position of those swollen eminences which 

 appear earlier than the clitellum, and are known as tubercula 

 pubertatis, offer further characters. In the following tables, 

 extracted from those of Rosa, the known British species of this 

 genus are grouped according to these three characters. With the 

 help of these tables and Figs. 199 and 200, any of the species 

 ought to be easily identified. 



WITH CHAETAE DISTANT. 1 



1 In the tables the figures refer to the segments of the body. Opposite the name 

 of each species are two sets of lines ; the upper series indicate the segments occupied 

 by the clitellum ; the lower series those occupied by the tubercula pubertatis. The 

 dots indicate the occasional extension of the clitellum or of the tubercula. 



