ZooL.— Vol. II.] EISEN—OLIGOCHALTA. 185 



Sfermathecal Sexual Set(s. — (figs. 50, 51.) Michaelsen 

 was the first to discover the sexual spermathecal setae in 

 Dtplocardia. These setae have been found in D. Eiseni^ 

 D. Udei, and D. Michaelseni. In the former species they 

 occur in two somites, VIII and IX, while in D. Udei they 

 are found in three somites, VIII, IX and X. It is interesting 

 to note that in the latter species somite X, which does not 

 contain any spermathec^, still possesses these sexual setae. 

 It is only set£e ah which are replaced by sexual setae. The 

 form of these is similar to curved penial setae: they are 

 much longer than ordinary set« and quite slender (fig. 

 150). The apex is strongly and beautifully sculptured, as 

 shown in figs. 151, A and B, Under a low power the sculp- 

 ture appears like bristles, but under a good apochromat we 

 see that what appears to be bristles are but short curved ridges, 

 each one enclosing a flat oval field with a granular sculpture. 

 There is no difference between these setae in IX and X. 

 Each one of the setae protrudes through a pore surrounded 

 by a pale elevated ring or circular ridge and the. body- wall 

 surrounding the two setae is elevated, appearing as if 

 strongly glandular. This causes the ventral side of somites 

 VIII, IX and X to appear much swollen and also wider than 

 the other surrounding somites. 



Glands of the Sexual Setce. — (fig. 154.) The external 

 elevation of the body-wall around the spermathecal setse is 

 connected with an interior differentiation of structure. 

 Michaelsen has described somewhat similar structures in 

 D. Eiseni, but judging from Michaelsen's description they 

 differ considerably from those found in D. Udei. Unfor- 

 tunately Michaelsen does not give any figures, so that a 

 minute comparison is not possible. He described them as 

 structures without distinct cell-walls, but with numerous 

 nuclei. I suspect that this absence of cell-walls may be 

 due to degeneration. 



In Diplocardia Udei I find that an extra layer of glandular 

 cells has made its appearance between the muscular layer 

 and the epithelium (fig. 154). Some of these cells protrude 

 between the muscular fibres, but the majority are pushed in 



