of Oligochoetous Annelids. 99 



The spermatophore of Limnodrilus, again, is of a different 

 shape, broad and rounded at one extremity, tapering at the 

 other ; that of JSfais is very long and thin, the spermatozoa 

 being simply twisted into a rope. In those of the Ssenurid^e 

 there is an axial canal filled Avith granular matter, or some- 

 times with shrivelled epithelial cells ; the spermatozoa are set 

 spirally round this canal, imbedded in the fii*m and tough 

 cement so that only their extremities project. These ex- 

 tremities in Tuhifex I generally saw in active movement 

 whilst still contained in the seminal pouch, so that they pro- 

 pelled the spermatophore in most elegant curves through the 

 water when liberated into it when this contained two per 

 cent, of sodium chloride. The spermatophores of Tuhifex 

 rivulorum were of all lengths ; sometimes quite short, little 

 longer than broad, at other times they appeared as long, 

 snake-like bodies ; sometimes they were incompletely cemented, 

 and sometimes the cement alone appeared to have assumed 

 the form without imbedding any spermatozoa. The sper- 

 matozoa themselves, when fully developed, are thread-like 

 filaments, without any distinct head, or rather with an un- 

 usually long and thread-like head, distinguished from the 

 much shorter and somewhat slenderer filament by no demar- 

 cation, but by its mobility : the short filament is continually 

 moving, bending over on itself, so as to give the appearance 

 of a knobbed extremity with any but the highest powers of 

 the microscope, since it remains in this reflexed position when 

 at rest. The cementing substance of the spermatophores is 

 probably secreted, to a large extent, in both Tuhifex and 

 Limnodi'ilus^ by the seminal vesicles of Claparfede, and in Cli- 

 telUoy where these are wanting, by the glandular portion of 

 the vas deferens. But it is clear that the thick cellular wall 

 of the spermatic reservoir itself also takes a part in forming 

 the cement, from the manner in which ill-formed spermatophores 

 are sometimes seen adhering to the sides of the sac. In Nais^ 

 moreover, the vas deferens is most minute, with no glandular 

 appendage whatever ; the simpler form of spermatophore found 

 in this worm is cemented entirely by the secretion of the walls 

 of the spermatic reservoir. 



The great distention of the spermatic reservoirs when filled 

 with these bodies has not been sufficiently dwelt on. Both in 

 Nais and Tuhifex they become greatly elongated, and extend 

 through several segments of the worm ; their development is 

 greatest in Nais. 



7. Genital Organs q/ Chaetogaster and Nais. — I have had 

 further opportunities of seeing the genitalia of Chcetogaster 

 limncei. The consecutive manner in which the various organs 

 of generation are developed in this worm is curious. Specimens 



