THE ANNALS 



MAGAZINE OF NATUBAL HISTOEY. 



[SEVENTH SERIES.] 

 No. 36. DECEMBER 1900. 



LXVIII. — A suggested Origin of the Segmented Worms, and 

 the Problem of Metamerism. By H. M. BERNARD M.A. 

 Cantab. 



During the last five years in which I have been working at 

 the stony corals, the Coelenterata, as an animal group, have 

 been more or less continuously in the foreground of my 

 imagination. I do not pretend to have seriously worked at 

 any other than the Madreporaria ; yet the fact just stated 

 will, I trust, be accepted as some excuse for the following 

 article. In it I propose to show how the Ccelenterates 

 may have given rise to the segmented Worms. The idea 

 forced itself upon me by its simplicity, and, although not 

 altogether new, it has never, so far as I am aware, been 

 stated as here proposed. I may add that I am still further 

 impelled to trespass beyond the region of my own serious 

 studies by perceiving that, if there is any truth in the sugges- 

 tion, it offers a possible solution to that vexed problem " What 

 was the origin of the mesoderm ? " 



In the geological record metamerism first appears in the 

 Trilobites, which are constructed of a number of segments 

 jointed together. With the exception of a head-piece and, in 

 most cases, a tail-piece, which differ from one another and 



Ann. & Mag. N. Hist. Ser. 7. Vol. vi. 34 



