390 On Alternate Generation in Annelids, 



parent stock given below (PI. X., fig. 1,) with that given 

 by Johnston, of ( Si/llis prolifera) the parent stock of the 

 European species. 



The synonymy of this genus will therefore be as fol- 

 lows : 



AUTOLYTUS. 



Autolytus (Grube), Wieg. Archiv. 1850, I., p. 310 

 (parent stock). 



Polybostrichus ( Orsted, A. S.), Gronlands Ann. Dor- 

 sib. 1843, q. a., {^ ) (preoccupied). 



Diplocersa ( Grube), q. a., { S )■ 



Sacconereis (/. Milller), q. a., 1853, ( 9 ). 



" (M. Mailer), q. a., 1855, ( 9 and $ ). 



Syllis [Johnston, Geo.), q. a., 1845 (parent stock). 



From what precedes it is seen, that there are known at 

 present three species of Autolytus besides that found on 

 our coast, and for which I have proposed the name of 

 Autolytus cornutus. They are Polybostrichus longosetosus, 

 from the coast of Greenland ; Sacconereis Schultzii, from 

 Trieste, and Sacconereis Helgolandica. There are good fig- 

 ures of two of these species ; so that I have satisfied my- 

 self that the species found on our coast cannot be identical 

 either with the species of Greenland or with that of the 

 German Ocean. As Max Miiller had ample opportunity 

 of satisfying himself of the identity or difi'erence of the 

 species from Helgoland and that of Trieste, there can be no 

 doubt of their specific difference. 



Autolytus cornutus resembles more in its general appear- 

 ance the S. Helg-olandica than the Greenland species. It 

 has a smaller number of rings than P. long-osetosus ; the 

 tentacles of the head are shorter. (The figure of Orsted 

 being that of a male, the comparison made here applies 

 only to the male.) The cirri of the anterior and posterior 

 rings are more equal in length, while in lofig-osetosus the 



