394 On Alternate Generation in Annelids, 



The anal cirri are more flattened than the dorsal, and 

 are as long as those of the anterior rings. They are 

 almost always wanting, dropping off a few days after the 

 separation of the female from the parent stock. 



The general appearance of the male is entirely different 

 from the female, (see PI. XL, fig. 8) : the body, instead of 

 tapering gradually from the middle towards both extremi- 

 ties, attains its greatest width much nearer the head, about 

 the 12th ring. The number of rings which are not pro- 

 vided with long setaB, and have short dorsal cirri, are five, 

 instead of six as in the females. The spermatazoa (PI. XL, 

 fig. 8, o), are found on the sides of these six rings only, and 

 extend also into the cirri, but never into the posterior rings, 

 as is the case with the eggs of the female which fill the 

 cavity on both sides of the alimentary canal for the whole 

 length of the body. The dorsal cirri of the male are shorter 

 than those of the female, both in the anterior and posterior 

 rings. The greatest and most striking difference we find 

 in the head and in the first ring. (See PI. IX., fig. 7 and 

 PL XL, fig. 8.) The two large tentacles which are placed 

 slightly in advance of the eyes, instead of being, as in the 

 female, simple tentacles having the same breadth and 

 rounded at the extremities, are very broad at the base 

 where they are united by a prolongation of the anterior 

 part of the head. At a small distance from the head they 

 bulge out, giving the two tentacles the appearance of hav- 

 ing been united and separated afterwards by a punch, the 

 two swellings almost meeting and leaving only a round 

 space between the two tentacles, which divide into two 

 branches (sec a' and a'', PI. XL, fig. 8) at the extremity ; the 

 inner side of this tentacle is thickly covered with minute 

 ciliae. The median tentacle, a, is much larger than that 

 of the female, and takes its origin farther back, directly 

 above the opening of the mouth (7n), between the two 

 large dorsal cirri {&). Directly behind the eyes we find a 



