224 Mr. H. C. Williamson on a Bifid Earthworm. 



by the resistance offered by the earth in the posterior 

 portion of the intestine, that is, the portion of the intestine 

 lying between the opening and the anus. The cells sur- 

 rounding the wound would become active, and a healing process 

 would be set up. It is probable that the earth would tend to 

 find it? way through tliis opening in preference to passing 

 through the rest of the intestine, and so the wound would 

 not readily be closed. From the continued activity of the 

 cells in the attempt to heal the wound, a process would 

 gradually be formed. The main mass of the earth would 

 probably continue to pass through this opening until the pro- 

 cess became almost as long as the portion of the body 

 between the point of lesion and the original anus, that is, until 

 an equal resistance was offered at the fork to the passage of 

 the earth along both branches of the intestine. The quantity 

 of earth would then be equally divided between the two ap- 

 pendages, half of it passing along each. From the fact that 

 the right-hand appendage is the shorter of the two, it might be 

 supposed that a greater proportion of the earth would still pass 

 along it, owing to its offering less resistance ; but the greater 

 length of the left appendage is compensated by the fact that 

 its inclination to the trunk is less than the inclination of the 

 new appendage to the same. The new appendage having 

 now much less work to do than previously, the active cells 

 at its posterior end would be enabled to narrow the opening 

 and form an anus. 



]Sone of the explanations offered above are really satis- 

 factory. It is probable that this earthworm existed as a 

 normal Lvmbri'cus, before the right-hand appendage was deve- 

 loped. The cause of the budding must be left undecided. 

 There is doubtless some connexion between the fact tiiat the 

 reproductive organs are so undeveloped and the presence of the 

 lateral bud. Whether the reproductive organs were from the 

 first undeveloped, and the bud represents an attempt at 

 asexual reproduction, or the reproductive organs atrophied in 

 later life owing to the budding process, can only be a matter 

 for conjecture. An interesting question suggests itself. 

 How did this worm manage to move through the earth V 

 It was alive when dug up. It would have no difficulty in 

 moving about on the surface, but it certainly could not have 

 readily burrowed in the ground. It therefore probably lived 

 on the surface or amongst soft soil and decaying vegetable- 

 matter close to the surface. 



My best thanks are due to Professor M'Intosh, Dr. Fulton 

 of Jbidinburgh, and Mr. A. T. Masterman, B.A. Cantab., 

 University of !St. Andrews, for valuable assistance and advice. 



