910 EEPOET OF COMMISSIONER OF FISH AND FISHERIES. [32] 



close to the efferent duct, generally in front of the same. In Telmatodri- 

 lus they extend even into the ninth setigerous segment, and take the 

 form of pear-shaped, sack-like bodies, of a rather larger size than those 

 of other species. 



In all the genera of TuMjicini, except in Uyodrilus, we find the ovaries 

 in the segment of the several porus, but in Uyodrilus they are situated 

 behind the cingulum, and in Uyodrilus sodalis in the nineteenth to the 

 twenty-second setigerous segments, nearly entirely covered by the testes 

 in those segments. 



The shape of the ovaries, and the place in the same where the ova 

 develop, vary in different species, to some extent at least, but are not of 

 sufficient constancy to be considered as good genus and species charac- 

 teristics. In Spirosperma the ovaries are very long and broad, some- 

 times triangular, with an ova developing at their anterior and broadest 

 end. In Uyodrilus we find the ovaries to be plate or dish like, concave, 

 covering the testes like a shell, and developing the ova in one of the 

 margins. 



In Limnodrilus ornatus the ovary is long, narrow, and ribbon-like: in 

 Limnodrilus Steigerivaldi, broad, lobed, and tapering at both ends, with 

 the ova developing in the middle of the organ. In L. Silvani the ovaries 

 are extremely long and narrow, thicker at one end than at the other, 

 with the ova also developing at the middle of the ovary. In Gamptodrilus 

 they are short and narrow, bent in a right angle, with the ova develop- 

 ing in the same. The form, but seldom the place, of the ovary is variable, 

 and, however interesting and important from an anatomical pointof view, 

 is of little value as characteristics of genus and species. 



EFFERENT DUCT AND COPULATIVE ORGANS. 



From the many different opinions and theories, supported by as many 

 different authors, on the true nature of the oviduct and the invagination 

 of the penis into the same, it is pretty evident that the subject is a 

 difficult and important one, and the more interesting because being 

 unique in the animal kingdom. Such eminent investigators as von 

 Siebold,* d'Udekem,t Claparede,| and Vejdovsky§ have all advanced the 

 opinion that the penis in Tuhifex, Limnodrilus, &c., is invaginated in the 

 oviduct, ai?d that accordingly both the spermatozoa and the ova are 

 ejected through the same external porus by means of two different organs, 

 the penis and the oviduct. All the above investigators have seemingly 

 agreed upon the porus through which the ova should have been ejected, 

 but in regard to the interior opening of the oviduct, through which the 

 ova should enter the same, not two of them have been of the same 

 opinion. 



^Vergleicliende auatomie, p. 228. 



tHistoire naturelle des Tubifex, p. 25. 



t Reclieixlies anatomique sur les Oligochs&tes, p. 23. 



§ Ileber Psammoryctes Zeitschr. f. w. Zoologie, Bd. xxvii, p. 147. 



