Th e Ea rth ivo rm s of I re la nd. 217 



and Alliuus. He has since added Tciragonuyus. The curious 

 point to be noticed is, that though Kisen created the genus 

 Dcndrobccna, he did not recognize the species which would 

 naturally fall under that generic designation, and hence his 

 perfectly natural and appropriate term has been quietly ignored. 

 It is my purpose, therefore, to revive the term first introduced 

 by Hisen, and to show which of the species hitherto placed 

 under Ltivibriacs and Allolobophora must be transferred to the 

 subgenus DejidrobcBua. 



In revising Bisen's genus, however, it will be necessary to 

 extend the characters considerably, since he included therein 

 only one species, and that, till now, a very badly described 

 and little understood worm. His diagnosis is as follows : — 



Dendrobaena, 11. gen. 



Tuberada ventralia in segmento 14 [ = 15 Eng. method]. 



Setic uhiqne aequo intervallo distantes, exceptis duabus sunnnis, qiiarum 

 intervalhim aliquanlo niajus est. 



Lobus cephalicus tres partes segmenti buccalis occupans. 



Referring to this subject, Dr. Benham says: — "Eisen was the first to 

 subdivide the genus Lumbriciis into subgenera, according to the relative 

 amount of dovetaihng of the prostomium into the peristomium. This is 

 accompanied by certain other characters, which have been held sufficient 

 to characterize genera in other cases. So that I have retained his sub- 

 divisions Lumbricus and Allolobophora; but as his genus Dendrobcena is only 

 distinguished from the latter genus in having all the setse equidistant, 

 and as all stages occurring in the separation are found in Allolobophora, I 

 agree with Rosa that we ought not to recognize it." 



Consequently the name has been dropped, and in Beddard's " Classifi- 

 cation and Distribution of Earthworms," 1891, and Rosa's " Revisione 

 (lei Ivumb.," 1893, is omitted from notice altogether. The statement of 

 Benham to the effect that every degree of separation of the setae is found 

 in Allolobophora is true till we remove the species which properly fall 

 under the genus Dendrobcena. Almost without exception do we find that 

 the species of Allolobophora, as classified by Eisen, which have the setae 

 widely separated, are dendrobaenic in character. It is true that I shall 

 have to deal with one exception, but this is due to the fact that we are 

 not yet acquainted with all the species that exist, and cannot therefore 

 assign those with which we are familiar their exact position. The 

 characters of the group will be better understood when the different 

 species have been discussed. Generally speaking, however, we may say 

 that the worms are rose-red or flesh-coloured, small, with setae more or 

 less widely separated, arboreal in character, or found usually in and 

 about decaying timber or tree refuse. 



We may take Allolobophora celiica, Rosa, as a type. Rosa's original des- 

 cription was based upon three living specimens received from Brest, in 



