ON THE ANATOMY OF ALLURUS TETRAEDRUS. 367 



it is formed by a mass of glandular cells, exactly like those of 

 the clitellum, which form a rounded mass (see fig. 5) through 

 which the vas deferens passes without losing its distinctness ; 

 there is no cavity into which the vas deferens opens. It appears 

 to resemble in every way a similar structure in Criodrilus, 

 which Benham 1 has more correctly spoken of as " prostate." 



Rosa's account of the organ in question differs from that of 

 Benham. My own observations indirectly confirm the descrip- 

 tion given by Benham. 



In Allurus the clitellum does not commence until the 

 22nd segment, whereas in Criodrilus it begins in the 15th 

 segment ; the " prostate " gland has, however, the same 

 minute structure as the clitellum, and has every appearance 

 of being a solid ingrowth of the epidermis. In the succeeding 

 segments, including those of the clitellum, there is (fig. 8) a 

 solid ridge of glandular cells on each side of the body, just 

 above the ventral pair of setae ; this ridge is continuous in 

 front with the " prostate " glands, and consists of a mass of 

 cells exactly like those of the prostate ; it is plainly connected, 

 as shown in the figure cited, with the epidermis. 



The ovaries 2 (figs. 2,5, ov.) are in Segment 13, and occupy 

 the usual position. 



The oviducts (figs. 2, 5, od.) open by a much plicated 

 funnel into the same segment; their external aperture is in 

 Segment 14 (fig. 1, $ ). 



A receptaculum ovorum (figs. 2, 5, ro.) is present in 

 Segment 14. Its cavity is continuous with the oviducal funnel, 

 through the disappearance of part of the septum. 



The oviduct, therefore, opens on to the exterior of the body 

 behind the male reproductive pores, as also occurs in Rhyn- 

 chelmis and other Lumbriculidae ; this arrangement is not 

 met with in any other earthworm, except Moniligaster. 3 



1 Loc. cit., p. 568. 



2 My specimen possessed an additional pair of ovaries in Segment 14. This 

 may or may not be an abnormal condition. 



3 Horst, 'Notes from the Leyden Museum,' 1SS7- 



4 Beddard, * Ann. and Mag. Nat. Hist.,' Feb., 18S6. 



VOL. XXVIII, PART 3. NEW SER. C C 



