1892.] 



AN ABNORMAL EARTHWORM. 



187 



Eisen ^ in Eclipidrilus has described three pairs of ovaries situated 

 on segments 9, 10, and 11 ; this statement is challenged by 

 Vejdovky ^, who maintains that the Oligochseta possess only a 

 single pair of ovaries which are never found on the segments behind 

 the oviducts (see fig. 1, ov.^-ov^). In like manner the last-named 

 authority would throw doubt on Lankester's ^ description of the two 

 pairs of ovaries present in Chcetogaster. 



Among the other genera of the Oligochseta, so far as I am aware, 

 only one pair of ovaries is developed ; this in the Lumbricomorpha is 

 usually situated on the 13th somite. But, as has been just pointed 

 out, at least eight genera may possess more than one pair, and, 

 further, in many forms the ovaries are developed on segments other 

 than the 13th. 



The following table shows the variation in the position of the ovaries 

 in those forms that possess two or more pairs of ovaries : — 



Somites. 



Accmthodrilus 



Eclipidrilus 



Etodrilus 



Lumbricusterrestris (?her- 

 culeus) (normal) 



L. herctcleus (Benham) . . . 



L. purpioreus and L. tumi- 

 dus (Bergh) 



Allolobophora, sp. ? (ab- 

 normal) 



Perionyx (two pairs | 

 varying from 9-16). J 



Pkreodrilus : 



Phreoryctes 



UrochcBta 



10. 



11. 



12. 



13. 



14. 



X? 

 X 



X 

 X 



15. 



16. 



17. 



18. 



From this table it will be seen that within the limits of the 

 Lumbricomorpha the ovaries are found to vary in position from the 

 9th to the 18th somite, the maximum number thus far known to be 

 developed being seven pairs. 



In front of these we find in my specimen the two typical pairs of 

 testes developed on segments 10 and 11. As these are without 

 doubt the serial homologues of the ovaries, the genital glands in this 

 worm extend from the 10th to the 18th somites. 



The genital glands are developed from and under cover of the 

 peritoneal epithelium, on the posterior face of the mesenteries of the 

 genital somites. And when we consider that the mesenteries, from 

 which the germinal epithelium arises, are present for each segment of 

 the body, and, further, that in most of its organs the worm exhibits 

 a marked metamerism, it at once suggests itself that in those forms 



^ " BclipidrilidEe and their Anatomy," Nov. Act. K. Soc. Sei. Upsala, vol. xi. 

 (1881). 



^ Syst. d. Oligochaeten, p. 144 : Prague, 1884. 



3 "The Sexual Form of Chafog aster;' Q. J. M. S. n. s. vol. ix. (1869) p. 272. 



