384 On Alternate Generation in Annelids^ 



and fingers can be bent back together quite as far as those 

 of man ; so that the error was occasioned by the unnatural 

 contraction of the flexor muscles, which are very thick and 

 fleshy, by the spirit in which the animal had been pre- 

 served. And it will be seen that this structure, as found 

 in the dead specimen, while most completely adapted for 

 climbing, would have almost entirely precluded the use of 

 the hand for any other purpose. 



Burt G. Wilder.] 

 Cambridge, July, 1862. 



Art. VII. — On Alternate Generation in Annelids, and the 

 Embryology of Autolytus cornutus. By A. Agassiz. 



O. F. Miiller, in his Zolilogia Danica, figures a small 

 worm (Nereis prolifera), in the act of reproducing itself 

 by division. For many years this mode of reproduction 

 among the higher Annelids remained unconfirmed, and 

 many authors, Ehrenberg especially, began to throw doubts 

 upon the observation of Miiller. He even went so far as 

 to establish a division among worms, founded entirely 

 upon the mode of reproduction by division such as had 

 been observed among Naidina (called by him Somatotoma), 

 in opposition to the others in which this mode of repro- 

 duction does not obtain, and to which Nereis prolifera 

 belongs. It was not until Quatrefages and Milne Ed- 

 wards had both observed a similar phenomenon in two 

 other genera {Syllis and My rianida), tha.t Miillcr's obser- 

 vation was placed beyond the question of a doubt ; and 

 when the same mode of development was observed by Sars 

 in Filog-rana, and after his observations had been repeated 

 a few years later by Schmidt in a second species of that 



