656 OLIGOCHAETA 



that this large anterior nephridium is really due to the fusion of two or three 

 embryonic nephridia (see p. 50). In the following segments the nephridia have 

 also a well-marked muscular duct, which is furnished at the end (and this applies 

 also to the first pair) within a rosette-shaped organ, which appears to be a gland ; these 

 cup-like bodies also occur in Onychochaeta. The nephridia commence in the fourth 

 segment; the first few pairs have a larger funnel than the following nephridia, and 

 in this agree with the ' mucous gland.' 



In the last fifty segments or so of the body the nephridia are provided with 

 a peculiar glandular caecum. This was described by PERKIER as opening separately 

 from the nephridium ; but 1 gave reasons (61) for believing it to be a glandular 

 appendix of the nephridium. Similar structures occur in other genera of Geoscolicidae. 



The reproductive organs of this genus conform to the type met with in other 

 Geoscolicidae. There are, however, only a single pair of testes; these lie in rather 

 an unusual position, in the twelfth segment ; it is not by any means an easy matter 

 to map the segments of the body in the anterior region ; the septa following the 

 four specially thickened septa which separate the segments immediately following 

 upon that which contains the gizzard, are very thin and are pushed back in the 

 middle, as is so often the case with earthworms ; the position of a given organ is, 

 therefore, difficult to ascertain ; in any case, the ovaries lie in the segment directly 

 following that which contains the testes ; and we know that the position of the 

 ovaries is much more fixed than that of many other organs ; it is, therefore, more 

 likely on the whole that the testes are abnormal in position than the ovaries. 

 I place the testes, therefore, in segment xii. The sperm-sacs are a single pair of 

 long 'tongue-shaped' bodies extending through a number of segments. Although 

 there appear to be only a single pair of sperm-sacs that are developed from two 

 pairs of outgrowths of the septa separating segments xi/xii, xii/xiii. Into the 

 twelfth segment opens also the two funnels of the sperm-ducts ; these are large 

 and folded ; the sperm-duct of each side passes along the body-wall to its external 

 opening, quite unprovided with any trace of a gland, on the border-line between 

 segments xx/xxi. The ovaries and the oviducts are so like those of other earth- 

 worms that they call for no special description ; there are three, or sometimes 

 (P. arenicola) two pairs of spermathecae ; these organs are simple elongated pouches, 

 lying in segments vi, vii, viii, and without any trace of diverticula. 



A remarkable fact in the structure of this genus, also found in Diackaeta, is 

 the swollen portion of the body near to the posterior extremity. This is figured by 

 SCHMARDA in P. arenicola as the clitellum. In P. corethruruu FRITZ MULLER noted 

 the same modified region of the body, which he described as being of a swollen 



