390 



OLIGOCHAETA 



difficult to understand, the perpetually frozen undersoil of thi 

 Arctic regions. Eisen has described a number of species fron 

 Spitzbergen, and Colonel Feilden recently sent me an exampl 

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

 also saw another specimen. The family is characteristic of th 

 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 j 

 England and Ireland, and probably more will be identified. 



There does not exist at present any comprehensive account 

 the British species of earthworms, though all of them a 

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

 the British forms belong to the genus Allolobophora, which ma} 

 be divided into two series according to whether the chaet; 

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

 clitellum and the position of those swollen eminences whic 

 appear earlier than the clitellum, and are known as tubercul 

 pubertatis, offer further characters. In the following table 

 extracted from those of Bosa, the known British species of thi 

 genus are grouped according to these three characters. With th 

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

 ought to be easily identified. 



With Chaetae Distant. 1 



A. putris 



A. constrirta . 



A. veneta 



A. octoedra 



A. cyanca (subsp. 



profuga) 

 A. rubida 

 A. mammalis . 



26 



28 29 



30 31 



m; 



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

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

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

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



