392 On Alternate Generation in Annelids, 



such a remarkable manner, from parent stocks in which I 

 could not perceive the slightest difference, that I satisfied 

 myself that these individuals, which seemed to have so 

 little in common, were only the two sexes of one species. 

 I have before me the drawings of a male and female of 

 this genus (Poli/bostrichus long-osetosus, Orst.) made under 

 the direction of my father in 1849, which are referred by 

 him to two different genera.* 



The female Autolytus cornutus (PI. IX., fig. 1), is a small 

 worm about one half an inch in length, of a flesh color, the 

 alimentary canal appearing as a green tube extending 

 from one end to the other; the posterior and the anterior 

 rings are of a greenish tinge. The cirri are also flesh-color, 

 and the eyes a dark chestnut-brown. The head has three 

 long tentacles, the longest {a) placed directly in front on 

 the middle of the head, and one tentacle, {a' a"), nearly as 

 long as the central one, placed on the dorsal side directly 

 in advance of the eyes, which are placed on each side of 

 the head. The eye consists of two lenses of unequal 

 size. This compound eye [h) is placed in an oblique 

 position, so that the larger eye is nearer the ventral side 

 and in advance of the smaller eye, which is placed nearer 

 the back, but farther from the anterior part. Directly be- 

 hind the eyes, on the ventral side, we find a tentacular 

 cirrus {c) about one third the length of the tentacle {a") ; 

 this cirrus is slender and placed on an exceedingly narrow 

 ring, which can hardly be distinguished from the head. 

 The next ring has a long dorsal cirrus (c'), fully as long 

 as the central tentacle (a), though somewhat more slen- 

 der. The six rings following have a dorsal cirrus [c") 

 of the length of the tentacular cirrus (c). The rings of 

 the body increase gradually in width towards the middle, 

 and then taper off" towards the tail. The dorsal cirri of 

 these six rings are all of the same length ; but beyond 



* See also Grube, q. a., avUo does the same. 



