688 OLIGOCHAETA 



The setae have the usual y-shape characteristic of the terrestrial Oligochaeta. 

 They are invariably eight in number to each segment of the body, and may be more 

 or less strictly paired. Occasionally (A. foetida, &c.) they are, as in Geoscolicidae, 

 ornamented at free extremity. 



The Lumbricidae also resemble the Geoscolicidae in that the clitellar setae are 

 commonly modified in shape, though they never exhibit the ornamentation so 

 characteristic of the last-named family. The setae in question are very much longer 

 and thinner than those upon the non-clitellar segments. In Allurus (at any rate 

 in one species of that genus) the clitellar setae have a spear-shaped termination. 



The clitellum in this family is always saddle-shaped, and it always occupies a 

 posterior position, never commencing before the eighteenth segment (Tetragonurus 

 pupa) ; in one instance (Allolobophora niolleri) it begins so far back as the forty- 

 eighth segment. These are the two extremes, and almost every intermediate position 

 is met with. 



Highly characteristic of the Lumbricidae are the structures first called by EISEN 

 the Tubercula pubertatis. These structures in fact, at any rate in the peculiar form 

 which they show in the Lumbricidae, appeal- to be confined to that family. They 

 are prominent papillae, sometimes paired, and sometimes taking the form of a pair 

 of bands running continuously over several segments. Their structure is like that 

 of the clitellum, and they appear before that organ on some of the segments which 

 will be occupied by it. Their position corresponds to the interval between the 

 dorsal and ventral setae, and, therefore, to that of the male pores with which they 

 are sometimes united by a groove, which has been noticed by several writers (e. g. 

 CEEFONTAINE). In two Lumbricids only are the tubercula absent ; and ROSA. (4) 

 has shown that in these two cases (Allolobophora eiseni and A. constricta) the 

 spermathecae are also absent. 



The male pores, excepting in the genera Tetragonurus and Allurus where 

 they are upon the twelfth and thirteenth segments respectively are upon the 

 fifteenth segment. The only other terrestrial Oligochaeta in which the male pores 

 occupy this position is the Geoscolicid Kynotus michaelsenii. Very commonly the 

 lips of the apertures are tumid owing to the great development of glandular 

 cells ; in the few species in which this is not the case the male pores are very 

 inconspicuous *. 



As regards internal structure the Lumbricidae are chiefly to be distinguished by 

 negative characters. The gizzard is always single and at the end of the oesophagus, 



1 This is duly noted in the descriptions which follow ; if nothing is said it is to be assumed that the 

 pores are prominent. 



