108 On a Bifid Earthworm. [Sess. 



V.— ON A BIFID EARTHWORM. 



By Mr J. T. MACK. 



(Read April 26, 1894.) 



The specimen of earthworm (Lumbricus terrestris) exhibited 

 was found by a friend of mine, Mr J. A. Thomson, Blackford, 

 Perthshire, while digging in his garden a year or two ago. It 

 has been dissected by Mr H. C. "Williamson, M.A., B.Sc, St 

 Andrews Marine Laboratory, to whom it was handed by Pro- 

 fessor M'Intosh, St Andrews. Mr Williamson says : — 



The specimen is an earthworm in which the posterior half of the bod} 7 is 

 double. Each of the posterior portions has an anus. The recorded cases 

 of bifurcation in the species of Lumbricus are few in number ; and while 

 that abnormality has been noticed not unfrequently in Polychseta, still 

 comparatively few have been described. Professor E. A. Andrews, of 

 Baltimore, U.S.A., published a list of the references made by different 

 authors to bifurcation in Annelids in ' Nature,' vol. xlvii., No. 1214, Feb. 

 2, 1893. . . . It is probable that this earthworm existed as a normal 

 Lumbricus, before the right-hand appendage was developed. The cause 

 of the budding must be left undecided. There is doubtless some connec- 

 tion between the fact that 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 ? 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. 1 



Mr Williamson, it will be noticed above, raises the question 

 as to how this worm managed to move through the earth, and 

 he assumes that it existed either on the surface or close to it. 

 Mr Thomson assures me, however, that it was at least one foot 

 beneath the surface when dug up. 



1 'Annals and Magazine of Natural History' for March 1S94, — which see for 

 other examples of bifurcation in the species of Lumbricus. 



