^^^7.] ANATOMY OF KARTHMORMS. 391 



body by being longer and thinner. In Urochceta one or more pairs 

 ol the fhtelkr setae are larger and beset with a number of tiansverse 

 notches. I have recently described an identical moditication in the 

 clitellar setae of the closely allied genus Thamnodrilus K Horst dis- 

 tinguishes - the clitellar =ette of llhinodrilus by their greater size. 

 In Lumbricus the moditication of the setae is not confined to the 

 clitellum, but is also found in the neighbourhood of the generative 

 orifices. 



I believe that in the genus Perichata no modification of the sets at 

 all comparable has ever been described except by niv^elf in P. armata 

 and P ceylonica. The first-named species is remarkable for the fact 

 that the termmal part of the ejaculatoiy duct opens on to the exte- 

 rior in common with a thin-«alled muscular sac, the interior of «hich 

 IS filled with a number of peculiar setae, the shape of which can be 

 best appreciated by an inspection of the figure «hich accompanies 

 my memoir. Perichceta ceylonica is the only other species of the 

 genus in \Ahich this arrangement is repeated, and the arrangement is 

 practically identical with that which obtains in P. armata. It is 

 perfectly clear that these sacs of penial setae correspond in every 

 way to the penial setae occasionallv developed in other Earthworms 

 tor example in the genera ^crt/i/^(;^nYi(s and Tijphceus. In Acantho- 

 drilus It IS certain that penial setae are not siipemumerary structures 

 developed only at the period of sexual maturitv, but thev replace the 



ordinary setae of the pair which corre.-poud to the male geneiative 

 aperture. 



EXPLANATION OF PLATE XXXIII. 



Fig. 1. Transverse section of vas deferens ; biglilj magnified. 



2. Testis (0 and vesicula seminalis (i\s). 



•6. Transverse section of oesophagus and central gland of 11th seament. 

 a, dorsal blood-vessel; *(, supra-intestinal (double); h, heart- h' 

 branch supplying walls of oesophagus and gland ; p, peritoneal coat.' 



4. bection through gland (rudimentary ovary ?) attached to wall of I3th 



segment, b, gland ; a, muscular tube enclosing it ; to the left the 

 tube IS seen to form a bend and to be cut across twice 



5. Central aspect of oesophagus in segments 10 and 11, to show suboesopha- 



geai glands (a). Bifurcation of subintestinal vessel illustrated in this 

 figure. 



6. Lateral view of same region. Bifurcation of supraintestinal vessel, as 



well as subintestinal vessel, illustrated. 



7. Transverse section of oesophagus in 10th segment; left-hand figure 



through opening of subcesophageal gland (highly magnified in fig 3) 

 nght-hand figure in front of or behind opening of gland. Conipare 

 with figs, o and 6. o o r 



8 9, 10. Transverse sections through prostate gland at various levels. 



11. Opening ot vas deferens funnel into vesicida seminalis. a, vesicula 



crammed with developing spermatozoa; c, ciliated funnel; b, vesicle 

 ot vas deferens. 



12. Section of oviduct, to show ciliated epithelium and muscular walls 



13. A portion of fig. 8 more highly magnified. I, lining epithelium • e' 



glandular cells ; m, transverse longitudinal muscles. ' ' 



14. Section of epidermis, a, problematical body ; b, glandular cells 



P. Z. S. 1«87. pt. i. » Not^s from Leyden Museum, 1886. 



