DESCRIPTIONS OF GENERA AND SPECIES 689 



lying therefore behind the calciferous glands. The latter appear to be invariably 

 present, but they have only been investigated in a few forms. I have already 

 referred to the curious fact that out of the three pairs only one communicates with 

 the oesophagus. ROSA (15, p. 15) has commented upon the differences in appearance 

 presented by the calciferous glands of different species. The intestine always has 

 a typhlosole. There is no supra-intestinal blood-ves'sel, and the last pair of hearts 

 are not situated further back than in the eleventh segment. 



The reproductive organs only vary in the number and position of the spermathecae 

 and in the position of the male pore, which has been already referred to. 



The testes are always two pairs in x, xi, and there are a corresponding number 

 of funnels. The sperm-sacs, as mentioned below, vary in the two genera Lumbricus 

 and Allolobophora. The ovaries, oviducts, and egg-sacs occupy the usual position 

 and appear to show no variation 1 . 



The spermathecae are spherical or oval sacs, absent only in Allolobophora eiseni 

 and A. constricta, which vary considerably in number, particularly in the genus 

 Allolobophora (q. v.). In no case has the spermatheca a diverticulum ; it is true 

 that in A. complanata I described some years back (13) an appearance of the 

 spermathecae suggestive of a diverticulum ; in fact, in several cases the spermatheca 

 was divided into two parts, one lying in front of, and the other behind the septum ; 

 but neither part could be called a true diverticulum of the other ; there was no 

 difference in minute structure, such as one always finds in a diverticulum, and really 

 no more than a constriction, covered by the septum, divided the two parts of what 

 is really one sac. The most aberrant species in point of its spermathecae is A. leoni; 

 there are here a large number of pairs of small spermathecae in a single segment ; 

 this is not necessarily, however, a point of similarity to the Geoscolicidae, in many 

 genera of which we meet with the same thing, since more than one species of 

 Perichaeta (see p. 428) is characterized by the same structural feature. 



Affinities. The Lumbricidae are in some respects a very isolated family, and, as 

 has been already remarked, they show a great uniformity in structure. There are 

 no aberrant forms to give any distinct clue to the affinities of the family. Never- 

 theless it seems, on the whole, that the most nearly related group is that of the 

 Geoscolicidae. And the principal resemblances between the two families are the 

 following : 



(i) The clitellum in the Lumbricidae is always saddle-shaped : nearly always 

 in the Geoscolicidae. 



1 I do not, of course, refer here to individual, but to specific variations. 



4 T 



