362 



OLIGOCHAETA 



the end of the spermiducal gland ; in the Perichaetidae the gland 

 is differentiated into two sections ; there is a muscular duct 

 leading to the exterior, and a lobate glandular part, which is 

 formed by a complicated branching of a single sac such as 

 exists in the Tubificidae ; in the Acanthodrilidae and in man 

 Oryptodrilidae the spermiducal glands are of a tubular fori 



and are not branched, though 



I 



w, 



fete^ 



-SjD.S 



there is the same differentia- 

 tion into a duct and a secretin < 

 portion. There are in the Acan- 

 thodrilidae two pairs of these, 

 and as many as three pairs in 

 Dichogaster ; in the latter casi 

 in three successive 

 In the Acanthodrilidae tht 

 glands are upon the seventeent] 

 and nineteenth segments. L 

 most Oryptodrilidae the sperm - 

 ducts do not open into the duct 

 of the spermiducal gland, but 

 on to the body-wall near to its 

 orifice, the distance varying in 

 different genera. In the Acan- 

 thodrilidae the male pore is 01 

 the eighteenth segment, re- 

 moved therefore by the distanc 

 rims, showing the generative f a segment from the apertur. 



segments. x 3. (After Hesse.) sp, 



Fig. 192. Diagrammatic longitudinal sec- 



Spermathecal pore 

 sac ; sp.s, sperm-sac 

 sac ; ?, female pore 



t, testis : s.s, seminal of 



either 



o, ovary ; e.s, egg- 

 6, male pore. 



of the glands. I 

 may be that a large series o 

 structures which exist in Micro 

 chaeta benhami 1 and in other Geoscolecids, and which have beei 

 termed copulatory glands, are the equivalents of the spermiduca 

 glands. 



In many earthworms there are, at the external opening of th 

 male ducts, bundles of specially modified chaetae, which have bee 

 called, from their supposed function, penial chaetae; they ar 

 usually ornamented at the free end with spinelets or ridges, and 

 frequently offer valuable specific characters. In the Lumbricidae 

 and the Geoscolicidae there are modified chaetae upon th 

 1 See Dr. Rosa in Ann. Hofmus. TVien, vi. 1891, p. 379. 



