124 



OLIGOCHAETA 



§ 9. Penis. 



The presence of a copulatory organ, more or less analogous to the vertebrate 

 penis, is not uncommon among the Oligochaeta. These organs may be single or 

 paired, retractile or non-retractile. Sometimes they are directly connected with the 

 male-ducts which open in them or on them ; more rarely they have no such close 

 connexion. 



In the preceding section, dealing with the spermiducal glands of the Oligochaeta, 

 I have described the terminal part of these glands, w^hich is almost always of 

 a muscular nature; in many worms this part of the tube is partly protrusible, 



perhaps it is so in most; I have 

 S- 3'- found that it certainly is so in Pen- 



chaeta houlleti, where a number of 

 specimens killed with alcohol had the 

 terminal part of the muscular ducts 

 of the spermiducal glands everted ; 

 I have not noticed the occurrence 

 of this in any allied forms, but it 

 very possibly takes place. In some 

 Perichaetae the muscular duct of 

 the spermiducal glands opens into a 

 wide and rather thin-walled terminal 

 chamber, which opens directly on to 

 the exterior ; it is here, again, possible 

 that this terminal chamber is pro- 

 trusible ; but I have no facts at hand 

 to prove or disprove the possibility. 

 In most Eudrilidae the two spermi- 

 ducal glands open into a single or 

 paired terminal copulatory apparatus, 

 which may be fairly termed a penis. 

 This structure, as has already been 

 pointed out, varies much in its development from genus to genus. It is very well 

 developed in Eudrihis; in that Annelid the terminal apparatus consists of a widish 

 chamber, opening directly on to the exterior; into this chamber open first the 

 spermiducal gland, and secondly the peculiar horseshoe-shaped 'glands' which are 

 figured in the accompanying woodcut (fig. 32). The spermiducal glands open on to 



TEBMINAL EFFEEENT APPARATUS OE EDDEILUS. 



pr. Spermiduoal gland. v. d. Sperm-duot. p. Penis, and 

 c. Otisliion like pad in interior of ' Bnxsa oopnlatrix ' which has 

 been cut open. 



